Need feedback on a "subadult" size rack

Hi guys,

I am buying my first rack this fall and have decided to go with c-serpents.
I am looking at the 5 slot subadult rack that uses sterilite 1655 tubs.

The sub adult rack will run me $335+ an additional small charge for a separate channel (I'd like to be able to have the top 3 slots on one channel and the bottom two on another channel).

I am planning on housing my 2 female sand boas and male hognose in the top three slots permanently, and using the two bottom slots temporarily to house my two female ball pythons.

I have 4 questions for you guys regarding this rack / tub size and would appreciate your feedback.

1. Is there a better / comparable iris or vision tub that would fit this size rack and would it be worth it to request that tub / pay the extra charge?

2. Up to what size BPs would you house in this rack size?

3. Have you had any issues when using a rack that has two different channels set up?

4. Would it be worth it to request casters or tub stops of some kind?

Thanks for your input and time!