I plan to install a 5" riser block on my Enco knee mill. The mill is in a corner where I can't easily get to it with my hydraulic engine hoist. I plan to fabricate the device shown below, and let the knee crank raise the head so I can install the riser. An advantage would be that I would be able to keep the head raised for whatever time it takes to do measurements, complete the riser block, and install it without having to hang it from lifting straps for a day or two.
One of the assemblies shown would be on each side of the table, sufficiently far apart to span the head. The two sides would be bolted to t-nuts in the table, and bolted together via a cradle shaped plate in the front and a flat cross piece at the rear.
I would welcome any opinions on whether this will work, or put too much strain on the knee screw or on the table. I don't anticipate having to adjust either the X or Y axes with the load in place. Once raised, I can block up the rear to help support it. The lift distance appears more than adequate.