I have several of a similar concept made by:
www.simplyrugged.com
Rob makes a truly simple and well made holster; not like the FIST #43 but like the FIST #14. You just have to pay the extra $10 to have it convertible to IWB and you are all set.
I personally dislike IWB. I only do so when I absolutely have to; and it does happen occasionally, but rarely. And when those rare occasions come up, just a couple of minutes putting on the loops and done deal. The minute that I am done with the IWB time, off come the loops and back to business as usual.
I have tried quite a number of different IWB holsters, mainly for 1911s, and the closest that I have come to "comfort" is my simply ruggeds. There are probably other diehard IWB guys that can help with "really good" IWB rigs, but as infrequently as I use them, having the convertible set up, that is still pretty comfortable as IWB, is the ticket for me.
Good Luck