You can find check valve holder from Heliproz. The line outside the fuse is for either using a clamp, or shut off valve (again, Heliproz) to cut off excess fuel from getting into the DZ after landing, to prevent flooding.

Belly pan quick release - you should be able to find them from World Models.

Flight Hobby Japan sells a very nice folding airplane holder, cost somewhere in the neighbourhood of $200.00.

Hope this helps,

Adrian