dave i am not an engineer and may be looking at this to simply but why couldnt you incorparate a large dovetail in your top frame and leg mechanisum that would allow the main sections to be pulled out and back in yet have some strength like the old slides had. the top insert could be connected threw pins and holes like the old tables did.. just a redneck engineering problly wont work but it might trigger your mind to somthing that will i hope .
If in Doubt, Build it Stout!
One hand washes the other!
Don't put off today till tomorrow!