Will this (bearing in mind its the .45 version) fit inside this?

I believe you would need this one. its the one I ordered but in 9mm to fit the Bravo size SC piston mount.  

I’m pretty sure the mount you would get if you selected .45 on the page you linked is the same item from the page I linked.

Product code is slightly different. One ends with a K and other does not.  Be careful

Just got an email back from Griffin confirming they’re the same item.

Would you mind measuring just the length of the spring of your 9mm version if you have the opportunity?

That's good to hear. Crazy how they can't keep their website straight, creates confusion or doubt. Sorry but I been waiting on the one I ordered to ship for 2 weeks now, still nothing. I wish I would have ordered from another company. On top of the fact that anything I get USPS is taking a min of an extra week to get. Fedex is another subject. I have a box that has been on the truck for delivery 5 times now. Sad thing is it's 30mins down the road.  Grrrrrrr  

Sorry for the vent.....