Most of the SIG C/L kits did/do come supplied with full size plans vertical grimace. i.e. Twister, Banshee. I'd have to pull the plans out for my Skyray 35 to check but pretty sure that it does too. Pretty sure even the SIG Shoestring (I bought one for a nostalgia build) and Buster do too. It's just the SIG Akromaster that doesn't. I can understand why, and the Akro kits were actually pretty cheap. The problem as you have identified is that so is the included balsa & lite-ply, and wood selection is a contradiction in terms universal to all SIG kits of recent years IME. One certainly won't find SIG contest grade balsa or ply in any SIG kit.
When I was a kid, all the Aeroflyte kits, our poor man's equivalent of SIG aimed at the entry and youth market, were similar to avoid 'sharing' and promote the sale of their kits. They came with a plan in profile and instructions, but ommitted the horizontal stab & elevator or a wing overlay relying upon notched increments.
Someone did CAD draw and publish a proper full scale plan and post it on the net for the Akro about a decade ago, but I think SIG acted pretty fast legally and had it removed. It's easy enough to manage an ersatz plan and trace the parts or just have and use an orginal as a pattern. I have both. A double scratchbuild is in the pipeline now. Such a capable, cheap, fun sport flier, it's worth the effort. I'd still stick with a solid profile fuse or composite assembly with lightweight spruce longeron. Use thin birch ply for the nose formers instead of liteply if you can source it. A 2oz R/C clunk works well with muffler pressure although so to do any of the former Smiths or Perfect design 2oz wedges now sold under the Brodak brand that fit the available nose space.