Modification gp88 to gp 300
open the gp88 file with hex workshop or other software
change number 23 with number 14 at offset 0000000C


3133 3354 5545 3439 3230 0403 2304 0102 <-- recognized as GP88 (original)
3133 3354 5545 3439 3230 0403 1404 0102 <-- recognized as gp300

write to the disk, finish.
run the program, and your gp88 recognized/detected as gp300 with features.