I agree with aerowoof, try the water and steam method first. The balsa will swell with the steam. Depending on the depth of the marks, it may not come all the way up to the surface. Final solution is to add putty or spackling compound.
ORIGINAL: aerowoof
those clamps look like overkill.I use spring type clothes pins for clamps as well as t pins or masking tape while gluing fuslage sides to formers.I also use x-acto bar type clamps and only use enough pressure to hold the piece in place not enough to crush.you may be able to remove those marks if you spray lightly with water let sit a minute then apply a hot iron.the steam should swell the dented areas as long as the fibers are not broken.repeat as much as neccasary