Although I can confirm Nero CD Speed: Overburning Test says overburning supported for YUDEN000T02 @4636MB, however in real life test using Nero CD Speed Create Data Disk and DVD Decrypter it failed. So BenQ 1640/BSKB does not support overburning and probably wont.
Pic1: Nero CD Speed: Overburning Test on YUDEN000T02 @4636MB (bug?)
Pic2: Nero CD Speed Create Data Disk Overburning Enabled @4600MB, stopped at normal capacity 4.38GB/4482MB.
Pic3: DVD Decrypter, attempt to overburn and stopped at normal capacity with Logical Block Address Out of Range error.
For comparison, overburning with Plextor PX-716A
Pic4. Nero CD Speed Create Data Disk Overburning Enabled @4630MB, success.
Pic5. Disk quality screenshot for Pic4 (no scan), showing 4630MB.