I have to agree with the OP. I hate lite-ply (an oxymoron) in models. It has the same properties as wet cardboard, not very strong and heavy. Otherwise you would not see all the ARF's using it with 90% of it cut away. While it is enough for air loads, it tends to self destruct with minor bumps with the ground.

However, the Sig LT-40 is such a great trainer, I can overlook the use of lite-ply. Though if somebody decided to just buy the wing kit, they could scratch build a balsa and ply fuselage.