Just yesterday I replaced my regular size (147DF) Futaba receiver that I had in my little Ultimate with one of the GWS 6 channel receivers. Test flew it and it flew fine. This effectively "freed up" my Futaba receiver for the next project......
I'm pretty much set on the APC 9X7.5 Slow Flyer prop for my Park 450. I've tried a bunch of different props and although I do like the APC 9X6E, the 9X7.5 gives a flight time of about 13 minutes on a 2100 battery, plenty of speed but it aint gonna 3D. I'm sure it would 3D with an APC 11X4.7, but at a major cost in flight time......and since I could care less about 3D it's not a consideration.
As for mounting the TP/Apex 2100 batteries, I'm just using a block of soft foam to fill the void between the firewall and the first former wedging the battery between the foam and the bottom of the fuselage.....and still "screwing around" with that battery door.
Take my word for it----on a partly cloudy day you'll be GLAD you got the purple one!