I have one of the LG-446 model on a sub compact 40 and two of the LG-445 for the XD-45's then one service 40 without a CT grip. I like them and my wife doesn't, she says it makes the grip too wide. I am too lazy to get into the safe right now, but if I remember correctly it is about 1/4" thicker with the grip on at its widest point. Installation takes about 5 minutes including reading the destructions.
I would suggest that you practice as much with the laser turned off (it has a power button) as you do with it on, just a Murphy's law thing.
This is a picture I copied from The XDtalk forum, this gun is not mine. It shows how the thickness of the grip changes. It may or may not matter to you. This picture is from a sub compact 40.
If you do buy a new LG-446 in the next month or two and do not like it, I will buy it from you for $150.00 shipped for my last XD without one, the last time I looked (about a year ago) they could be found for about $180.00 new. I know that isn't a good deal for you, but I will throw it out there for a plan B option.