i can confirm that the BTC 40x upgraded to 48x works just fine.
In fact with the writing mode changing to P-CAV i found that some of my old Princo 32x cd which were only writing at 24x now write at 40X P-Cav ie starts at 18x and steadly climbs to 40x with an average write speed of 31.5x
Audio ripping speed also has shot up from the 24x to 31.43x
Definately work doing the upgrade
Thanks Brandon & Cyril