I looked into editing the presets but I can't seem to add it. Was trying to add the no_ball attribute to negative since they make the balls on trans chars bigger, but I can't figure out how to do that. Editing base female presets didn't do anything.
You could extend the blend_penis.lpcharacter file.
But first make a futa npc what you like, save as preset then copy the relevant values to this file.
After that this will be the default penis type for futas in your game in the future.
Quick tutorial on a value inside of it, for example on the 'PENIS TAB_Gen3F_27097__Very Long: 100% -0.3=>0.1' line:
'PENIS TAB_Gen3F_27097__Very Long' - is the morph name
'100%' - is the chance to be applied (100% always apply, 0% never, and between them self explanatory)
'-0.3=>0.1' - is the range of morph, final value will be random between the min(first) and the max(last) value
The format should be always looks like this example. (morphname, chance, minmax)
As I remember the beauty standard settings isn't bother this morph value so that wont override.