it sounds as though they are built a little different. not sure there will be room for something like that. the tank extends right through to F3 which is just under the front window. i've got my throttle control just behind that.
i like the colour scheme you found for yours. i've seen those fire bombers before and there is another one up here in canada(see attached) with a rather unique colour scheme that i might do. they are all 802's though...haven't seen many 502 looking any different.
are you going to spray your plane using paint and a clear afterwards?
ORIGINAL: SIMCO
I got looking at maybe using flour with food dye for coloring and a small mix of sand or grass seed for the heavier material to come out straiter. SWIXTT man I don'twhat size the interior of the airship is for hopper size. If the 72 is built like the 100 with the gas tank box you could make a false firewall and shove every thing in throttle,gas tank on a traythru the front end. might give more interior room. Cg shift was my big concern,dropping 2lbs off center tends to balloon or pitch down. This is the paint scheme I was going to do . I know it's not a 502 but the general ideas are there.