1) You can do different sizes of TV if you a) move the mount, b) change the mount out for an articulating arm mount, c) use VESA adapters to move the mounting holes higher for bigger TV (Link
I used the arms for one of those Sony PS3 TVs, just because I had one sitting around. See the attached pics.
2) Do yourself a favor and get a small player instead of trying to lug DVDs around. You can get little media devices that let you store and play content directly, like a Roku with a small external hard drive attached. You can just mount/glue it to the back of the TV and then you don't have to fuss with physical media. There's free software to rip your DVDs, if you have a large collection (check out Handbrake, it's easy to use and 100% free).
3) I second the bins. I use a mix of bins with the swinging lids for "permanent storage" and some collapsing crates (Link
) for things that are used at the track/campsite and only put away when it's time to leave.
4) Few random tips:
I use a rack on the back of the bathroom door for towels, tp, shower supplies.
Get some retractable ratchets to reduce the headache of dealing with straps (Link
Make sure you take care of yourself at the track, as in, get some comfy "zero gravity" chairs, a decent music player, etc.
There are cool accessories you can get for the "utility track" in the awning. Everything from LED lights to full misting systems to keep cool. Have fun googling options.
You can grab a 5-6 watt solar "battery tender" charger that you can leave plugged into the "solar ready hook-up" on the side of the Pup to keep the battery charged without big cables criss-crossing your driveway.
Alternatively, sometimes I keep my pit bike (Honda Grom) and both track bikes in the trailer with the RV power plugged into my house power (with one of these Link
) and then have all three bikes on their own battery tenders inside the trailer. That way, all four batteries are being topped off in one location.
If you're doing dirt, I would also highly recommend some heavy duty mats to scrape mud