My husband just modified a garage sale table for me like this: He cut a hole to fit my machine. He took a board a little bigger than the hole and using carriage bolts hung it right under the hole. These carriage bolts are long enough, 4"-5" or so, to make the shelf adjustable for any machine. They do show on the top of the table but are rounded smooth and shiny. They could be recessed into the top, but I didn't want him to bother with that. He cut 1" off the legs because I'm short. The shelf adjusts with bolts and there are rounded caps on the ends so nothing will catch on them.
We are looking for another cheap ($20 or so)table or two so he can modify some to sell. We're hoping to get $75-$100 for a nice big sewing/quilting table. I live in Central NY.