Hi Richard & Robin. Thanks for your help.

I kept my fingers crossed and experimented with a simple
write (2,'(a70,f10.5)') copy70, thickness

format statement. Surprisingly, the 3rd party binary accepts it! After
all my hard work to left-justify it and make it cosmetically similar to
a working input file. So yes, the "FPDE" errors were due to a column
width mismatch.

I will look up the trim & eor statements. Sounds like useful things to
know about.