Starting a build

Hi all - After hours of reading through all the threads in this forum, I'm about to start building a new enclosure for Robert. I've done a bit of woodwork before, so I'm fairly confident with the basics, but I have a few things I'm pondering that I'd love some input on. Thanks for any help!

First, based on the wood I'm using (1/2" Maple ply leftover from another project) and the base it will sit on, it could be either 5ft x 2ft x 3ft tall, or 5ft x 2.5ft x 2ft tall. I've already got a 36in T5 fixture and bulb that I want to mount inside along with the basking light, so that might play into which is best. Any thoughts on which would be better??

In terms of ventilation, I plan on following the advice from some of you to put small round vents low on the cool side and higher on the hot side. I'm also considering putting a screen panel in the lid, and/or vents along the top back. Would that be overkill?

Finally, I have a bunch of 12x12 slate tiles I could use for flooring. I have ceramic tile in his tank right now that are loose to remove for cleaning. I find that water, etc, sometimes seeps between them, which isn't a big deal as it's glass underneath, but I worry about it with plywood (I do plan to seal it well, but water sitting on plywood, no matter how well sealed, can cause problems). Has anyone else had issues like this? Should I grout the tile? And should real slate tile be sealed (I know real stone can be porous)?

I'd go with the taller option so you can provide more climbing spots. The top vent is fine. Probably not necessary if you have the side vents, but it won't hurt to have it. As far as the tiles go, if you check under them regularly then moisture probably won't be an issue, but if you set them and seal them they should still be easy to clean and water won't get through. It will make the enclosure even heavier if you have to move it though.

You could use non adhesive shelf liner under the tile and just wipe that down when you pull up the tiles to clean.