You can add it like this:

for example 0.1
1) type a 1
2) type a . before 1

or 1.1
1) type a 11
2) type a . between 1

Sorry, there is a little problem in typing decimal values, I'll try to improve that.

Thanks So much for the reply and the Mod, this works really well, thanks. Cant wait for the planned updates to custom armour and ammo types, keep up the great work!