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.