How much shrinkage is there in 703 when u wrap it in burlap

Hi all, i am in the process of making superckunks and side wall / rear wall absorbers: (see thread -http://www.johnlsayers.com/phpBB2/viewtopic.php?t=8459 ) My question: is there significant shrinkage to a 2' by 4' sheet of rockwool or corning 703 / 705 when you wrap it in burlap or something similar? I am building timber frames for all my absorbers and i want the absorbers to fit snuggly inside them - ie. i don't want any gaps visible around the edges of the sheets. i was thinking of making the frames 5-10mm smaller than the sheets on both the y and x axis. I have designed the frames so that they fit the sheets as i don't want to be cutting them where possible. I would also appreciate any comments regarding the design of the layout if possible? Thanks

spacecho Just a thought: Isn't it safer to buy first the wool and then make some simple tests if you really want it nicely clamped? These sizes have some tolerances. The way you pack them will influence it etc.

When I built these http://www.bobgolds.com/Absorber/home.htm I made the inside dimensions 2'x4' (to 1 mm) -- and I had to push the rigid rockwool in. Roxul (the manufacturer) said they were 2'x4', and that's what they were.