Been through this one. I am 5'10" 200lbs., stocky but no big gut (yet), but have short arms, 44 short in coat size, (this aint my bio so ya'll be patient). Have my M25 sniper clone and AR15HBAR equipped to take the Harris. Bought the LM6-9 first. Not a good thing for me prone (which was the whole reason for buying a Harris....bench rest shooting I use a, uh, benchrest). The 9-13 did the trick, can use it collapsed in the 9 on a bench or extend it prone. World of difference for me, especially shooting anything with an extended mag. My rec: get the leg notch model, LM-9-13, if you have any size on you, and if you feel a bit wild, get the swivel base (I've been told this is the it thing, but I'm simple and don't shoot much on uneven ground). Best bet would be to get the 6-9 AND 9-13 and return the one that doesnt work. Let us know how it works. Happy Thanksgiving!
Cleophis