MTK

For the fuse to weigh that much with no FW and floor, you probably had one of the heavier fuses.

The new FW doesn't need to weigh more than 20 grams for a motor. Maybe less. You should be able to cut some of the area out.

Built up wing might weigh less with very close watch on balsa type. If you can get a set of laser cut ribs to your specs, the rest is straight forward.

Or a new larger foam core sheeted with 1/32 stock would work at least as well. I'd use 6-8 lb density. I've sheeted wings before with 1/32" stock and that works fine, You will shave an ounce plus off each panel.

I've settled on a different approach for sheeting...I start with 1/16" and taper sand to 1/32" at the tips before installing on the foam. It's a lot of dust but the weight saved is real. My sockets are always installed using half spars top and bottom, extending to the sheeting. Forms an "I" beam structure which is stronger and lighter than anything else I've seen. The half spars extend beyong the end of the socket by at least 3" eliminating the stress at the end of the socket. The spar stock is 1/8" balsa with grain running spanwise.

Consider the weight....my typical wing panel is 500 square inches. I never use plastic film on pattern models; silkspan and paint only. A panel typically weighs in at 12 1/2 ounces ready for gear. Or around 15 ounces ready to fly. Some, very few, can use plastic film and bring weight down a little more. However, most wings these days are at most 400 square inches per panel... Your choice...

Such ismy current design flying with a DLE55 up front: 530 squares each and 430 grams each RTF...Plenty strong enough for a 55cc engine...Good luck