So, said file should be named glide_shp.tbm? Or even psn_shp.tbm (assuming 8.3 convention)? If so, that still doesn't work.
Editing ships.tbl directly doesn't work either, it complains about just about everything being moved, IE: I expected this and got that (where that is the next item up from what this is)
Here's the contents of said file, just in case I managed something wrong, though the provided example is pretty clear:
$Name: GTF Ulysses
+nocreate
$Max Velocity: 70.0, 70.0, 70.0
$Rear Velocity: 70.0
$Glide: YES
$Name: GTF Hercules
+nocreate
$Max Velocity: 50.0, 50.0, 50.0
$Rear Velocity: 50.0
$Glide: YES
$Name: GTF Hercules Mark II
+nocreate
$Max Velocity: 55.0, 55.0, 55.0
$Rear Velocity: 55.0
$Glide: YES
$Name: GTF Ares
+nocreate
$Max Velocity: 50.0, 50.0, 50.0
$Rear Velocity: 50.0
$Glide: YES
$Name: GTF Erinyes
+nocreate
$Max Velocity: 65.0, 65.0, 65.0
$Rear Velocity: 65.0
$Glide: YES
$Name: GTF Loki
+nocreate
$Max Velocity: 75.0, 75.0, 75.0
$Rear Velocity: 75.0
$Glide: YES
$Name: GTF Pegasus
+nocreate
$Max Velocity: 90.0, 90.0, 90.0
$Rear Velocity: 90.0
$Glide: YES
$Name: GTF Perseus
+nocreate
$Max Velocity: 80.0, 80.0, 80.0
$Rear Velocity: 80.0
$Glide: YES
$Name: GTF Myrmidon
+nocreate
$Max Velocity: 75.0, 75.0, 75.0
$Rear Velocity: 75.0
$Glide: YES
$Name: SF Mara (terrans)
+nocreate
$Max Velocity: 15.0, 15.0, 75.0
$Rear Velocity: 0.0
$Glide: YES
$Name: GTB Artemis
+nocreate
$Max Velocity: 65.0, 65.0, 65.0
$Rear Velocity: 65.0
$Glide: YES
$Name: GTB Artemis D.H.
+nocreate
$Max Velocity: 65.0, 65.0, 65.0
$Rear Velocity: 65.0
$Glide: YES
$Name: GTB Medusa
+nocreate
$Max Velocity: 50.0, 50.0, 50.0
$Rear Velocity: 50.0
$Glide: YES
$Name: GTB Ursa
+nocreate
$Max Velocity: 45.0, 45.0, 45.0
$Rear Velocity: 45.0
$Glide: YES
$Name: GTB Zeus
+nocreate
$Max Velocity: 55.0, 55.0, 55.0
$Rear Velocity: 55.0
$Glide: YES
$Name: GTB Boanerges
+nocreate
$Max Velocity: 55.0, 55.0, 55.0
$Rear Velocity: 55.0
$Glide: YES
#End