There are several things that affect the ability to cut . Even a fingerprint on one of the windows (or mirror or lens) will do it. The lens is dished on top and domed on the bottom. Having the correct height is also mandatory, the proofgrade mark will assign a height that should be correct, but any warping will mess that up so it needs to be firmly held down ideally with bedpins you can make yourself.
Maple has the least char of the many species, but there is some carbon that needs to be cleaned no matter what wood you are using.