A little historical correction.
The LCPR was NOT a progression in the Higgins line. LCPRs were built by
Chris Craft because Higgins refused to have anything to do with the
design, which was from the Navy's BCR (Bureau of Construction &
Repair). He felt it was too heavy forward, which increased the boat's
draft and was not a welcome characteristic when moving over
sandbars. The book you mentioned covers this (and is a must-read
for any Higgins boat fan). BCR wanted Higgins under their thumb and
tried their own design but his ramp was much better and that's why the
LCPR wasn't built after 1943 or so while the LCVP line ran the rest of
the war.
Also, the early technique for putting the ramp on (cutting the bow off
of a LCPL) was done because it was actually easier for them to do this
than to stop the line and retool it to build them with the ramps from
the start. This was changed at a later date, I believe when a new
factory was brought on line.