ICORE Rules at times are "loose" shall we say? 6.10 says A revolver may only compete in a single Division that must be declared prior to the start of competition. I interpreted that, at local matches, to be you can't sign up to shoot multiple divisions with the same gun at once, meaning you can't sign up in Open/Limited with the same Revolver and just shoot once. Locally we've shot up to 2 Divisions with the same Revolver so we can double our primer usage! And not slow down the squad.
As for moon clip holders, try to find (or make them) Kydex Holders like North Mountain made.
https://www.revolversupply.com/moon-clip-holders/ might still sell some and they allow you to use the same holder for all of the moon clips.
As for moon clipping the .44's, I'd probably not do it again. Finding RN bullets for the .44 for ICORE are a pain and the moon clips that I got were loose and easily damaged.
I've not used the magnetic holders, so you might need to find someone who does have them and find out. I'll see if I can't contact a buddy who would know.
The longer the barrel the less the sight picture requires refinement. There's a reason dot shooters like shorter barrels, less weight out front to stop on the next target and less movement if they have to go into a port. With a Dot you're not hindered by a short barrel, with iron sights a longer barrel will have less bullet dispersion for the sight picture.
I'd recommend skipping moon clipping a .44 and go with a 929, unless you can find a 6 1/2" M25 that may take a longer search.
If you load your own rounds you're welcome to shoot my 4" M29 with or without moon clips.