JGA,
Regarding the size, if it is going to be in the shop 90% of the time, I would say go the full 4x8 size. The size of the table you mention using as your base seems as though it may be a bit small for stability unless you are going to somehow mechanically fasten the tops and base (I still think you would be cantilevered quite a bit to make it a sturdy bench though). Also, the first bench I made I did without using any rabbets or dados. The butt joints are fine as long as you glue them it just takes a bit longer ensuring spacing and allignment, and can be a little messy. I don't see any reason to use dominos on this bench. Flatness should never be a concern with this design.... You just need to ensure a good sturdy base. Just my $.02.
Nate
Regarding the size, if it is going to be in the shop 90% of the time, I would say go the full 4x8 size. The size of the table you mention using as your base seems as though it may be a bit small for stability unless you are going to somehow mechanically fasten the tops and base (I still think you would be cantilevered quite a bit to make it a sturdy bench though). Also, the first bench I made I did without using any rabbets or dados. The butt joints are fine as long as you glue them it just takes a bit longer ensuring spacing and allignment, and can be a little messy. I don't see any reason to use dominos on this bench. Flatness should never be a concern with this design.... You just need to ensure a good sturdy base. Just my $.02.
Nate