Philbert, I have only two easy suggestions to make:
(1) Increase the length of the bottom to add a couple of inches in height. Leave the cross pieces the same width.
(2) Counter bore holes about 3/8" deep for the bolts, nuts, and washers to bury them (and then use a shorter carriage bolt) so that the saw's chain can't ever hit them.
Good ideas. This is my 'mini-buck' - I have a larger one that puts the wood between my knee and waist height. Recessing the bolts or using 'T' nuts would also be a good idea for general use; could also use brass instead of steel. I know that the bolts are there and only cut on the outside of the legs, or directly in the middle, and the saw usually cuts through the log 3 - 4 inches above the bolts. But I am sure that if I loaned it out . . .
Philbert