This looks like a lot of work but it's really not bad. Somewhere between a built up balsa wing and a sheeted foam core. The reason to go through the process is weight saving. This wing will come in around 3 oz./sqft ready to paint. A balsa sheeted foam core wing would weigh about 40% more and if I had sheeted this wing with balsa it would weigh about 20% more.
In the photos I've added and shaped the 1/4" balsa LE and started work on the ailerons. I'm going to cover the wing with kraft paper which will shrink as it dries imparting a lot of stiffness to the wing. But you either have to leave the DT foam TE quite thick or reinforce it somehow so it doesn't bend. I glued 3mm bamboo to the TE and sanded the foam down to it. (I found a bamboo roll up blind at the home center a while ago and now I have a lifetime supply if 3 mm bamboo sticks.) That should give a nice thin, durable TE.
In the past, I've shaped the tips from solid foam but the edges tend to get beat up quickly. I've been making tail surfaces for a while now from two layers of foam with hardwood veneer between
. It allows me to sand the edges very thin and yet still be durable. I thought I'd try it on the wing tips. The center of the edge of the wing tips isn't a flat plane as in the tail surfaces, it's a curve. I derived the shape of the curve and hot wire cut it in a block of foam. I traced the tips on some 1/16" balsa and glued the block back together with the balsa in the middle. When the glue was dry I roughed out the shape on the bandsaw. I'll glue those onto the wings and do the final shaping before covering.