hi Cutty,
the compression block will only really just compress the outer fibers, they need to be heated up to work best, and i do believe that they will lower the spine a bit- but will give a nice glazed. polished look!
This is quite different to the compressed "Forgewood" shafts made by Sweetland!
where the entire wooden blank was compressed to 1/2 or more of its original size!
This process , made a very dense, very strong, very high spine shaft of extremely small diameter!