Thanks for moving it into the right forum, Adam. Yes, the plan is to mate it with an 8" dome. I only ever plan to use it at very shallow depths (in a pool), so I'm even considering taking it to a machine shop to have a bit shaved off from the inside if it's too tight a fit.
Here's the response I got from Ikelite regarding this lens:
Based on online specs, that lens would be a very tight fit in the FL port system. The diameter limit is 3.3”. If the lens length is 3.5” it would probably fit in a # 5511.2 port but I would recommend a longer # 5511.3 port which will definitely fit and generally provides better edge sharpness.