I decided to try CloneBD 184.108.40.206 on a Doors - Live at the Bowl '68 concert disk. It created an 25 Gig ISO image on the first try! I made a Full Clone (default settings) as I want the Menus to work - except I selected the Audio Core Option to reduce the compression of the Video (with a smaller targeted Audio File). The Resulting Size said it was 20.67 GB.
However, when I went to Burn the image with Alcohol 120% to a BD-RE test disk, the Image was too large. So I tried a BD-R LTH Type and got the same error. So I tried a "normal" BD-R and got the same error. (All 3 disk types are Verbatim.)
I tried it again with Img Burn and it failed on all disks. The Image was 25,381,437,440 (24,205 Gigs) whereas all the Disks were 25,025,314,816 (23,866) all according to Img Burn.
When I toggle the Target Size now, and try Custom just to see if I can adjust it (you can), but when I go back to the default 25 GB Destination Setting, the Resulting Size said it now was 23.25 GB. So there's something Flakey there.
I just set it to 22.85 GB using Custom so we'll see where that takes us...