On the SPAD originals page, the only pure 4mil B combat design seems to be the Defender. You don't have to stick to known designs, though. Sift through the data, pick a wing design that you think you can build, a fuse design from another plane, and stick them together.

You can build an RNAF (Dogfighter) style wing out of 4mil. It's not as easy to do as it is with 2mil, but if you crease the snot out of it at the leading edge, and have a helper, flat table, board, and lots of clamps, you can do it. I've also folded a simple Debut-style wing with 4mil. It wasn't easy, and you may want to consider using mechanical fasteners like zip ties to hold the trailing edge together. The wing feels like it'll take any amount of abuse, though.

The QHOR isn't a very good plane for streamer combat, if that's what you're up to. It's more adept at hover sumo. No offense, Demon