As someone who has worn heavy handguns literally hundreds of hours in the field, I can tell you that generally speaking belt rigs are most comfortable for guns with barrels under 6"s. If you are having issues with your pants getting pulled down (and that is not at all an uncommon issue) then a very practical and comfortable solution, is to use suspenders that attach to the belt.
I use Dickies suspenders with hooks that attach under the belt. The wide elastic straps are very comfortable and distribute the weight on my belt quite nicely. I have been using them for hunting for quite some time, and used similar ones for when I used to work, carrying a bunch of stuff concealed on my belt (gun magazines, radio).
https://www.amazon.com/Dickies-Perry-Suspender-Black-Size/dp/B001VNBAYA/ref=sr_1_6?crid=3G1UQNUFPRF5V&dchild=1&keywords=suspenders+with+hooks&qid=1629985354&sprefix=suspenders+hook+to+%2Caps%2C259&sr=8-6
The Hill People Gear kit bag is another option. However, as a user, I can tell you that having had one a few years now, it takes a fair bit of practice to deploy a handgun from one quickly. You are unzipping it from a bag on your chest, then withdrawing it. This takes repetition to do quickly and efficiently. Most guys I know who have these, never actually practice and are slow as crap with them. If you get surprised by an animal, well you may not have the typical 5 seconds it takes most guys to get a gun out and onto target with one.
I am not knocking the HPG bag, as I like mine. I am simply giving a real world, practical report after using one for a number of years.
Seriously not trying to give you a hard time here, but your experience carrying a large revolver in the field is not likely relevant to what the OP needs.Going on a raft/float trip, a belt holster is pretty much the least useful. The reason chest holsters are popular up here, is that given the weather, we are almost always wearing different layers of clothing/ raingear, and having the pistol on the outside, and not under the long tails of coats is far more useful.
As for the bag on the chest... the deployment scenario of those is kinda funny when talking about dealing with a charging bear. I've been charged (false charge), and know others who have been charged by brown bears. Usually, when it happens, it is a surprise in low visibility brush. On my false charge, I had less than 1 second notice to deploy my Redhawk. There's simply no time to fumble around with a bag, or search under your long jacket for your belt holstered pistol.
The following video is VERY annoying, and edited stupidly... fast forward to the guts of the video, and ignore all the slo-mo replays.... Just concentrate on the few seconds of actual action from 2:00 to 2:04:
https://www.youtube.com/watch?v=vUG8UPsgE3UOk then,,,,, your comments above on this situation are "SPOT-ON", and looking at that Video, the 1st mistake that guy made, was not pulling his Gun, and being
in the READY as soon as those Cubs came into view, he got lucky, I was in the same type of situation a few yrs back, down on the Branch-River, ie... (Alagnak River), it ended alittle different,,,,, Bear Floating in the River, and shortly thereafter, some Levelock Boys just happened along,,,,,, coming up-stream, said they heard the shots, 3 of them, and asked if we wanted the Bear,,,, and I said it's all yours, they put a rope around one hind leg, and motored back down, from wench they came,,,,, and this wasn't my 1st Rodeo on that River with this type of Chit going on,,,,, again to anyone reading this Post, the 1st indication of any Bear, Cub or otherwise, you need to be clearing-leather pretty "Dam" Quick, as my Granddad used to say......
Lj