The tables are 30" high to match all of the other tables we have.
To support the machine from below: (1st photo below)
First measure the height of the machine sewing deck to the table top it normally sits on. (deck height)
Next on each side of the new table 1. allow 1/2" for MDF table top and then measure down the side of the table (deck height). Draw a line there. Next measure down another 3/4" more to allow for the board that will lie flat from side
http://www.quiltingboard.com/t-112333-1.htm to see pictures on pp. 1 & 2
I had been using a plexiglass extension for my machine, but the heavier projects had a tendency to cause the extension to slide around and move.
I started looking for tables that the machine sat down in and created a flat working surface. But, boy are those things pricey.
I decided to try and built one myself. Went to Home Depot, bought 1 8ft 2x4, 2 8ft 1x6 and a 2ftx4ft piece
I would never do them that way. You end up with bias edges on all the edges. Cut the squares bigger, draw the line down the center and sew a quarter inch away and then trim them down. The rule is to add 7/8ths of an inch but you can add an inch or even an inch and a quarter and the square them up to perfect.
Buy this, you'll never regret it, from Bear Paw Productions. She's wonderful to deal with.