I'm not planning a mapper version of sfall now nor ever, but I've looked up the relevant memory addresses if anyone else wants to patch it in.
Point these at a bigger block of memory: 4C0347, 4C045B, 4C0658, 4C0671, 4C2E53, 4C2E5D, 4C2EB4
And increase the value of these: 4C035F, 4C0477...