chucky:
I, too, upgraded from a Roo 19 to a 2503S!
Here are the mods I've done:
1. Inside switch/pilot light for hot water heater electric element (Post #13)
http://www.forestriverforums.com/for...-110742-2.html
2. Honeywell RHB111B digital thermostat (Post #2)
http://www.forestriverforums.com/for...tat-98522.html
3. Fencepost sewer hose holder (Post #10)
http://www.forestriverforums.com/for...ge-107199.html
4. PVC pipe WDH spring bar holder (Post 11251)
http://www.forestriverforums.com/for...0726-1126.html
5. BAL Hide-a-Spare for spare tire (Post #1, 2, etc)
http://www.forestriverforums.com/for...ite-91088.html
6. 2” receiver/beefed up frame for bike rack (Post #12 for my Mini Lite; Post #2 for my Roo)
http://www.forestriverforums.com/for...-107358-2.html
7. 4 pin connector for bike rack lights
8. Routed fresh water tank drain to side of trailer (Post #5)
http://www.forestriverforums.com/for...ank-97264.html
9. 110VAC outlet on street side sofa table (Post #7)
http://www.forestriverforums.com/for...ns-110682.html
10. New locks all keyed together (except outside shower)
11. Dura Single Handle faucet in shower
12. Replaced on-board water filter with coupler and outside filter (Post #3)
http://www.forestriverforums.com/for...ng-122170.html
13. Accu-Rite fridge/freezer temperature monitor (Post #86)
http://www.forestriverforums.com/for...-129003-9.html
14. Computer fans on fridge condenser coils (no pics)
15. Removed rubber feet on Murphy Bed legs and replaced with felt (no pics) You should have the 5/8" plywood floor, so not as big a deal for you. UPDATE: Just realized you have a 2013 with the luan-foam floor, so you may still want to do this. Check to see of the feet have made indentations in the floor.
Here's some other items (and a repeat or two):
http://www.forestriverforums.com/for...3s-149155.html
Good luck.