I'm a sucker for .375s--and all big bores in general for that matter. I have a Marlin .375 Win., the previously mentioned T/C in .375 JDJ, a custom, high number 1903 Springfield sporter (1950s vintage) in .375 Whelen, three H&H Mags (2 Model 70s--a 20" post '64 and a 23" pre '64--and a Brno 602 with a 25" barrel), a .375 Ruger Hawkeye African, a Remington 700 SS/Synthetic .375 Ultra, and the two Steyr .376s (a Scout and a Pro Hunter). And don't get me started on my .38-55s.
The .375 Whelen has a 24" barrel, and it gives about the same performance as the short barreled .376s.
To be honest, I've not used RL17 in anything, but you've got me thinking about it. Once some of my other loading projects are finished (I've been working with both the .338 Lapua and the .338 Ruger Compact Magnum--with the latter a possibility for this year's elk quest in timber), I'll try to experiment with RL17.
I had a .378 Weatherby some years back, but I fell out of love with the wood stocked Mark V rifles and got rid of all of them. I've since been picking up the Mark V Ultralights, though, and I'm very pleased with them (when you do a lot of walking, hiking, and climbing, every ounce counts). My .257 Ultralight "electrocutes" antelope, and it's been on four "one-shot" hunts since I got it. I'm also partial to my .338-06 Ultralight, and I'm sorry they dropped the caliber.
Keep 'em in the black.