Very cool. I will warn you that this tank is long and heavy. It took two people to cary it into the house. Also water is heavy so this setup will weigh around a thousand pounds when filled with water. Our house is on a concrete slab so weight is not an issue for us.
My turtles are smaller than your slider so I have not tried to build my own basking area. I use large Zoo Med floating docs for my map and painted turtles.
These are what I use: https://www.amazon.com/Zoo-Med-Turtle-Gallon-Tanks/dp/B00178LI50
They also make an extra large floating doc for larger turtles but I have not tried it out: https://www.amazon.com/Zoo-Med-78098-Turtle-X-Large/dp/B01AYBRVN8
I do not have a sump on the tank. I just run the FX6 and a UV sterilizer. Also the FX6 and power strip barely fit in the center compartment of that stand.
I used to use a syphon kit that I bought from the pet store to drain the water but that was expensive and a bit slow so I bought a cheap pump on Amazon and purchased a pipe to hose adapter at the hardware store. I start up the pump and let it run for a few minutes and then detach the hose so I can get the hose into the hard to reach corners of the tank.
Pump I use (it has a lot of different adapters for various tubing but no hose adapter): https://www.amazon.com/gp/product/B0018X2XT4/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
The adapter I have looks similar to this one except the one I have is male hose thread to 3/4" female pipe adapter (you can find these adapters in the irrigation section at Lowes and Home Depot): http://www.homedepot.com/p/DIG-3-4-in-Female-Hose-Thread-x-3-4-in-Male-Pipe-Thread-Swivel-Adapter-50007/100186564
I clean out the tank about once a month and clean reusable media and swap out filter floss and polishing pads. Even after a month my water is still clear and my ammonia and nitrites are at 0 but my nitrates are in the 40-60ppm range.
Older pics (pump I use with the adapter is in the second to last image in the gallery): https://imgur.com/a/2c4d0
Even older pics: https://imgur.com/a/xOieq