ORIGINAL: c/f
If you cannot pass fully through the fuse the strength and weight advantage of tubes are lost IMHO. You might consider how Byron did the Mig in which the wings were the female side pocket of a plywood plate extension tab coming off of a fuse bulkhead around the fan. I redid a Byron MIG and remade that bulkhead former out of C/F (carbonfibre) It might be possible if that bulkhead were to be aluminum or some laminate of materials wood/c/f. You could get a wing pocket by using a combination of aluminum angle and flat stock needed to get to the desired u shape for tab insertion, I'm sure the wing pockets could be made as strong as the structure they ultimately glue too.
Actually Cermark viperjet has aluminum pockets that might by retrofitable?
hey, look at the BVM Rafale .. a short wing tube on each side of the fuse .. not even 5" into the fuselage.. thats all that plane uses for supporting the loads off of all that wing area on those delta wings ... the plane is one of the most solid planes out there. Its all about how well the load is spread out from the wing tube receptacles through the rest of the fuse ..
Voy