Correct. 120mm is the max. cutting height at the special cutting position.
Holding the guard slightly up is pretty simple since the guard has square holes for tying, but I don't think it's a safe practice or advisable to start the saw with the guard up and the blade exposed.
In a mock-up (with the boot removed for illustration) shown below, I was able to position the saw in the normal manner (without raising the guard beforehand) for a chopping (not sliding) cut on a 5" wide stock:
[attachimg=1]
Maybe your stock is a lot wider than 5"?