I have to edit this as my wording is terrible, shouldn't comment from a ipad
I would have to disagree with you in that MDF is not the ideal choice as it has to be perfectly sealed, and if not it will swell to double if it gets any moisture in that area. Plywood is much more stable especially if the correct type is selected amd if you went that extra bit to seal the edges underneath. Plywood is the classic as it lasts, MDF can not be fastened that well with screws as it will separate the layers so relies heavily on glued joints (not water based) and if it takes some knocks will delaminate as well. MDF machines does nicer and is smoother to prep (apart from the ends as will suck in the multiple coats of sealer) but that's about it.
As for Brims The last i bought off them was 8 years ago so maybe they closed doors but the name did come up in a search based in Brisbane. Mister Plywood is another good plywood supplier and can make custom ply and are located in NSW and QLD and they have the classic 3/4" ply thickness? Ensure you go for a laser ply or similar as then the sheets will be perfectly flat, use better glue's, no knots and is nice to machine. Cheap construction ply is crap of interior ply will be only have good layers on the outer surfaces and not in the centre - hence the warping.
http://www.misterplywood.com.au/
Also consider Stern did a few pin like the check version of Ironman etc in mdf as well as the The Pin and these are meant to be home pins and never sited and reckon after a few sales will not last the 30 years of use and transport like many of the old Gottlieb's. Ballys and WMS still with us.
Go for quality.
Hope that helps
