hi  after 20 plus years of building -i have my own way to join wing halfs- first when the wing half is first built -do be sure when you remove it from the building board (wing should only be tack glued )-and- before the final gluing is done that both the T/E and L/E are as straight as an arrow-  if not twist and crack it until it is-then move foward -to sheet it etc .-you must have no warps in  any control surfaces-   i always replace the wing joiner with  a 1/4 inch -5 ply  plywood-(at the L/E  also  )  when i  join the wings-  and sheet over -the center four ribs-  i have never had a wing joint fail on me doing it this way-and  there is no need to glass the center of the wing- as any of the heat shrink coverings do not stick well to epoxie from my experience  -i always reinforce my landing gear area with 1/4 inch -5ply plywood  and -or  1/2 inch half round hard wood  (i get at a lumber yard ) between the fuse floor and its sides-the only time my gear has come off-has been in a major crash in  my first two year of learing to fly RC    i build all my servo trays from 1/4 inch by 3/8 hardwood-had very bad luck using the plastic trays-if a kit gives you a piece of  1/8 ply for a tray -i then put the 1/4 inch by 3/8 inch hard wood below that -so the servo screw have wood to bite intothese planes and engines vibrate alot-put you hand on the side of a fuse when the engine is running-you wiil be surprisedi have seen aircraft come down from a flight with more than one servo scew that was almost unscrewedso do tighten your servo screws as part of you maintenance schedule  -lets say every 10-15 flights