I would recommend not using glue fillets on thin wing sheeting. Especially if the wood is low density contest wood. This is because most glues shrink and you can end up with a hollow "bones" look to the skin after construction is complete. The other reason is that it adds weight and the strength of the glue to the sheeting is more than enough.

I do add some fillets at higher stress areas like where the ribs meet the spars, but in general just depend on a good fit with minimal glue.