Okay, you're right, electricians often encounter situations requiring creative bending. While not electrical code related, we understand the challenges of working with conduit. Here's an assessment of your proposed method and some alternative suggestions

Assessment of Your Come-Along Method
Potential Issues



Kinking

EMT is relatively thin-walled. Over-stressing the middle with a come-along can easily lead to kinking. Kinking weakens the conduit and distorts its shape.

Uneven Bend

Achieving a smooth, consistent 1/2" warp over 10 feet using a come-along will be extremely difficult. You're likely to get a sharper bend in the middle than you intend.

Spring Back

Steel has "spring back." Even after bending, it will try to return to its original shape. This means you'll need to over-bend it slightly to account for this, and it's hard to predict by how much.

Safety

Using a come-along in this manner can be dangerous if the conduit slips or the come-along fails. Ensure you are working with appropriate safety equipment (gloves, eye protection) and keep others clear.

Potential Advantages



Low-Cost (Maybe)

If you already own the trees and the come-along, it's inexpensive in terms of materials.

Alternative Methods (Better)1. Conduit Roller/Bender (Modified)



How it Works

Conduit rollers, sometimes called "pipe benders," are designed to create smooth, consistent bends in pipe or conduit. They typically have a series of rollers that gradually deform the material. The larger ones are hydraulic, but for EMT, manual versions exist.

Modification for Your Need

You might be able to very slowly and incrementally put a slight warp by making a series of shallow bends as you feed the EMT through the roller. This takes patience and careful control. If you're careful you may be able to produce the desired effect.

Rental

Renting a conduit roller is a good option if you don't want to buy one.

Upside

Good control, relatively smooth bend.

Downside

Requires specialized equipment, may take practice.2.

Leverage Bending with Weight and Spacers



How it Works

This involves using a long lever (a sturdy piece of lumber, for example) and carefully placed weights to apply pressure to the EMT. Place the conduit on two supports (sawhorses or similar) about 8 feet apart. Position the lever so that it applies pressure to the middle of the conduit. Start with very light weights (sandbags, buckets of water) and gradually increase them. Check the bend frequently.

Spacers

Place thin wooden shims or spacers underneath the conduit near the supports to help control the bend.

Upside

More controlled than the come-along, uses readily available materials.

Downside

Still some risk of kinking, requires careful monitoring and patience.3.

A Chain (Careful)



How it Works

Drape the EMT over a low, stable support, creating the desired warp. Use a chain (like a tow chain) and drape it over the midpoint of the EMT, and apply gentle force.

Upside

May be the easiest

Downside

Hard to predict, requires careful monitoring and patience.

General Tips for Any Method Lubrication

Applying a lubricant (like WD-40 or a specialized pipe lubricant) to the inside and outside of the conduit can help reduce friction and prevent kinking.

Slow and Steady

Apply pressure gradually. Rushing the process will almost certainly lead to problems.

Multiple Passes

It's better to make several small bends than one large one.

Inspection

Carefully inspect the conduit after each bending stage for signs of kinking, flattening, or other damage.*

Consider Alternatives

Is there a way to achieve your goal without bending the conduit at all? Can you use flexible conduit, different fittings, or re-design the project slightly?

Recommendation

I would recommend trying the Leverage Bending with Weight and Spacers method first. It offers a reasonable balance of control, cost, and availability of materials. The chain might work and is easy, but potentially more dangerous due to lack of control. If that proves too difficult or the results are unsatisfactory, then consider renting a conduit roller. Avoid the come-along method if possible, as the risk of kinking and uneven bending is high. Good luck! Flag for review