I need to make a 4" riser block for my Delta Benchtop Mortiser and am
wondering about the suitability of MDF to cut and stack between the
base and the post flange?

Will it compress significantly to make my mortises out of square?

The replacement bolts will take the majority of the torque from the
mortising, but I'm not worried about those. I just need to support the
post.

The other option would be to elevate the entire base by 4 inches, but
that would interfere with the Y movement of my xy table.
Any thoughts, suggestions, etc. would be appreciated.

tillman