I run my return with the same style flex hose from Eshopps. No issues in 4 years and flex hose should allow for any misalignment so not sure what you mean by "Tension".... actually this will apply no stress to the rigid pipes and is a great thing when it comes time to yank your roller for cleaning or maintenance. While its true the serrations or ribs on flex hose can trap some bubbles, it just takes a little longer to purge the bubbles and will in no way I can think of be an issue. I'm moving approximately 1200 GPH silently through 3' of flex hose. Again, I've been running my roller for 4 years. Anyone saying you need to replace that hose with rigid is just running their mouth.....lol
I rigid plumbed my first tanks because it was thought to be the best way, but after several builds I asked myself why and can't find a good reason. I'll go one step further and say you actually need MORE flexible hose on your setup, specifically I'd get some for both connections to your UV pump. You have the right idea with your return pump, but your UV pump is likely to transmit vibration and/or noise to the tank. It also looks like its going to be a pain to pull that UV pump for cleaning or repair. In this case I'd use silicone tubing in the diameter your UV needs to flow at (I assume 3/4" if targeting Ick).
Will you be able to change your UV bulb without too much trouble? They only last a year but I find the tubes can get a coating of crap and reduce efficiency if the quartz isn't clean. I had to clean my quartz often until the tank matured and became stable.
My first tanks looked great but were a pain to work on due to rigid plumbing, I love the ease of flexible tubing for maintenance, something not often thought of in the excitement of assembling a new system.
Get that tank wet!....