@jstotz - You can use a sidemount light in a backmount configuration. As you're in the Great Lakes, go with the largest capacity battery so that you can run heat. 6 degrees is good. Look for constant power output.
I dive backmount (CCR) and sidemout (OC) with an UWLD 40 light and a tall SM canister (90 degree bend). Most of my diving is cave with an annual Great Lakes splash.
Buy a light with a power switch and adjustable level controls on the light head from a company that can customize the cord length. I don't think you can do better than UWLD for multiple reasons, but you can try other folks who live and breathe advanced diving. Whatever you do, avoid Chinesium.
Ask the manufacturer about customizing the cord length for your sidemount setup. A knowledgeable customer service person will tell you how to measure the cord length. Send out the light and the measurements and you're done.
Sidemount setup will fit you well if you took the measurements correctly. For backmount, decide where you want to mount the light. You can mount the battery on the belt or the CCR can or on a 3L cylinder. The cord will go under an armpit. You can also mount the battery below the can if you have a stand, then the cord will be routed "sidemount" style.
If you have extra cord, store it so that it does not drag. Note, if the light has the power and output level controls on the light head, then you can place the battery anywhere.
And now the pitch. You
want need UWLD because:
- You can get custom cord length
- The battery can does not have latches which won't rub (and potentially damage) other equipment
- The power and output controls are on the light head
- You get constant power output
- You get an ability to stack light and heater controls on the same battery
- You support an honest small business that is actively involved in cave diving community
- If you have questions or issues, Bobby, the CEO, will personally handle your matters
- Excellent product quality
Avoid Tecline. The company is in EU and the service logistics may be bothersome due to the recent geopolitical developments. Go local.