I'm looking at buying a G21 Gen4 for daily carry off duty. I was wondering if anyone had a picture of the different backstraps with the frame. Curious to see if there's a big difference and what the smallest one looks like. Is the smallest comparable to the former "SF" size grip? I've been surfing the web and just can't seem to find the info. My planned carry is this with a TLR-1 in a DSG Alpha series holster. I love the 45 and with the grip force adapter, I see this as being a good compliment to my 1911. Thanks for the help.