You've got a good plan! Here's a breakdown of your idea with some tweaks and additional considerations

Your Plan - Detailed & Refined
Spreader Bar/Adjustable Bar Hanger

This is the right approach for secure mounting. Make sure it's designed to support the weight of your pendant.

Key Considerations



Joist Spacing

Measure the exact joist spacing. Many bar hangers are adjustable, but you want to ensure you select one that fits.

Weight Rating

Overkill is better than underkill. Even if the pendant is lightweight, a robust bar hanger will provide a more secure and professional installation.

Offset

Is the existing wiring centered in the hole? If not, get a bar hanger that allows you to adjust the electrical box position along the bar. This ensures the pendant hangs where the customer wants it.

Mounting Type

Some bar hangers are nailed to the joists; others screw in. Screws are generally more secure.

Electrical Box

You'll need a box that can be securely mounted to the bar hanger.

Type

Get a box rated for ceiling fan/fixture support. It will be more robust.

Mounting

Ensure the box has the correct mounting hardware to attach securely to the bar hanger.

Wiring

Properly secure the wiring entering the box with cable clamps (Romex connectors).

Medallion

Essential for covering the hole.

Material

Consider the overall style of the room and the pendant fixture. You can find medallions in various materials like plaster, polyurethane, or wood. Polyurethane is lightweight, easy to install, and paintable.

Size

Carefully measure the diameter of the existing hole and the canopy of the pendant. The medallion must be large enough to completely cover the hole and allow the pendant canopy to sit flush against it. Err on the side of slightly larger.

Installation



Preparation

Clean the ceiling surface around the hole thoroughly.

Adhesive

Use a construction adhesive specifically designed for the medallion material and ceiling type. Apply it generously to the back of the medallion.

Fasteners

Even with adhesive, consider using a few small finish nails or screws (countersunk and filled) to further secure the medallion, especially if it's heavy.

Caulk

Caulk the seam between the medallion and the ceiling with paintable caulk for a seamless look.

Step-by-Step Installation Process1. Safety First

Turn off the circuit breaker for the lighting circuit you're working on. Verify the power is off with a non-contact voltage tester.2.

Remove Old Fixture

Carefully remove the existing can fixture. Disconnect the wiring, taking note of how it was connected (usually black to black, white to white, ground to ground).3.

Prepare the Hole

Clean up the edges of the hole in the ceiling as best as possible. Remove any loose debris or crumbling drywall.4.

Attic Access

Go into the attic and locate the joists around the hole.5.

Install Bar Hanger

Position and install the bar hanger between the joists according to the manufacturer's instructions. Ensure it's centered over the hole (or offset if necessary).6.

Install Electrical Box

Attach the electrical box securely to the bar hanger.7.

Wiring

Run the existing wiring into the electrical box and secure it with cable clamps. Make the electrical connections (black to black, white to white, ground to ground) using wire connectors.8.

Test

Temporarily turn the breaker back on and test the wiring with a test light or multimeter to ensure proper voltage and that you have correctly identified the hot (black), neutral (white), and ground wires. Turn the breaker off again.9.

Medallion Installation

Apply construction adhesive to the back of the medallion and carefully position it over the hole, centering it on the electrical box. Press firmly to ensure good contact. Use finish nails or screws if desired.10.

Caulking

Caulk the seam between the medallion and the ceiling.11.

Painting (if needed)

Paint the medallion and caulk to match the ceiling.12.

Pendant Installation

Install the pendant fixture according to the manufacturer's instructions, attaching it to the electrical box.13.

Final Test

Turn the breaker back on and test the pendant fixture.

Important Considerations & Alternatives Ceiling Material

What kind of ceiling is it? (Drywall, plaster, etc.) Plaster ceilings can be more challenging to work with and require different techniques for medallion installation and securing the bar hanger.

Attic Accessibility

Is the attic easily accessible? If not, this job becomes significantly more difficult. You might have to cut a larger access hole to work comfortably.

Existing Wiring

Inspect the existing wiring for damage (cracked insulation, etc.). If it's old or damaged, you might recommend replacing the wiring back to the nearest junction box.

Customer Expectations

Confirm with the customer that they understand the appearance of the medallion. Show them examples if necessary.

Weight of the Fixture

You mentioned it's lightweight, but double-check the fixture's actual weight. This is critical for selecting the right bar hanger and electrical box.

Alternative to Medallion (if possible)

Could a larger pendant canopy be used to cover the hole? This is often the cleanest-looking solution, but it depends on the pendant style and the size of the existing hole. Custom canopies can be fabricated, but that's typically more expensive.

Why this is a good solution



Safety

Addresses the need for secure mounting, especially important with any hanging fixture.

Aesthetics

The medallion covers the unsightly hole.

Compliance

Uses proper electrical boxes and wiring practices.

Professionalism: Provides a clean, finished look.Good luck with the installation! Remember to take your time, be thorough, and prioritize safety. Flag for review