How fancy you want to get on shaping the planks to more closely resemble airfoils is up to you. But truthfully it won't make any difference to the flying in the end. However by removing a lot of the wood you will both make it a bit lighter and a lot weaker. If the goal for this is to fly it only occasionally and with care then no problem. If it's to train a newbie or three then it's a bad choice to get too aggresive. But given all the requirements for finish this sounds like it won't be used for newbies. So sand away.
Tissue and dope would be my suggestion. The tissue adds strength and seals over the grain all at the same time. For a true show finish I'd suggest a coat or two of sanding sealer made using thin clear dope and talcum powder. A coat or two of very thin clear to seal the wood Then apply a coat of the sanding sealer and let dry well. This mix sands beautifully and fills well. Start with thin clear and add powder until it's about like cream. Work it into the wood but not too much or it'll "curdle" as the solvent flashes off. After sanding apply another coat of medium thin clear to seal the sealer....
Then apply tissue, dampen it with a very light water mist so it goes limp and use raw thinner to re-melt the last coat of dope and seal down the tissue. It may blush but that's OK. The next coat of sealing clear will cure that. But it shouldn't blush unless you're doing this on a really bad day. From there it depends on what you want for a finish. Either apply color dope or wait for it to finally stop smelling and then use some other form of finish or you may opt for an all tissue finish and clear dope for a different look. Both options can look great. The coloured tissue will be lighter but that's your choice.
..... at least that's how I'd do this. Especially if this is intended as a show piece.