Thanks Daniel, the original base board would have been 2.5x bigger and times two of them....that was a LOT of real estate!
Nice work Jim , I have a friend that wants to make a #20 deluxe & is wanting to know the base size....would you mind measuring them for me please 
G'day Bruce,
The dimensions of the original boards (both the #20 & #55) are exactly 500mm x 400mm and I have taken a closed up of the routed edge.
(Attachment Link)
(Attachment Link)
Thanks Jim
I have passed the information along & he is very grateful 😉👍