RE: us aircore
I was given an Aircore 40 trainer kit with out instructions.
I built it with no dihedral as a tail dragger, and using Spad techniques it came in at 4.5 pounds
( You should see the pile of unused coro parts left in the box, gotta be 2 pounds of them)
With a ringed OS45f 2 stroke, it flies great, floats for ever and can even do a fair flatspin.[8D]
Jeff
ps.
I added 1/2 inch of cord to all the control surfaces.