I'm thinking I can use the Kenai on a T-shirt but under another larger T-shirt or some light outer shirt. But I'm wondering where to carry extra mags.

With the HPG chest bag, carrying extra mags seems easier (and can also carry the FRS radio). But, well still thinking about the cons here.

Still deciding -- but thanks again for all the great suggestions. Some good options here.

And maybe I need both -- open carry in OR/WA. Concealed in CA/ID/UT/NV. Although I could use the Kenai for both (but still need to figure out how to carry the extra mags. I think 4 mags of 10mm won't exactly be light).

I keep mine in an outside pocket of my hydration pack when biking or when hiking in touristy / move traveled places, or OWB or a chest rig if on my property or in the outback. I can get it out of my little hydration pack quick enough if I need to. I think this also helps in the event of a bike wreck which happens once in a while outdoors... keeps it protected.

I have been mountain biking since time began, and have done it in, I think now, 37 states. In that time I have never ridden with someone serious with a chest pack. And that's thousands and thousands of other bikers. You simply cannot carry enough water and spares that way comfortably. And the older I get the more spares I want. A simple trip maybe. I don't feel any real problems getting the gun out of my hydration backpack, since I'm going to have to dismount anyway. I can and do swing the pack in front of me to get something but I don't see that working well with a gun and I've never really tried it. Anyway I continue to recommend a hydration backpack with pockets that suit your needs.

For rough use, i'd get either an LBT or HSGI, with a flap. Something that is "jumpable" if you are mountain biking.

Taking a spill and losing a firearm isn't ideal as well as full protection against the elements.

In my over 200 years of riding mountain bikes on multiple planets I have never seen a serious rider using a LBT or HSGI either. Sheesh.

Plus, how can I carry spares in a holster?

Tactical Tailor Lunar or a Hill People Gear kit bag.

I use a Lunar on a variety of packs while I'm cycling and the HPG is good too but I use it mostly for hiking. You'll need a true waist belt to use the Lunar, a Camelbak Mule or similar won't work.

I have carried a snubby 357M in the rear pocket of a jersey too but a Glock 20 will protrude.

Didn't you hear? Serious riders won't use a chest pack to carry a gun apparently. This has been confirmed in at least 37 douchebag states.

I hike a lot, but mtn bike only a few times per year. I use a HPG chest pack for my Glock 20. It's always been the most comfortable way to carry when you want to free up your waist and legs for maximum movement.

The only downside is that it gets hot.

Thanks guys -- I'm likely going to get all three:

1) HPG Recon and TT Lunar for concealed
2) Kenai for open carry (OR, WA)

Between the three, I think I'll be covered. I'll look at camelback's too - don't have one (been averse to the bladder thing).

Averse to the hydration bladder?

Hydration packs and their bladders with bite valves are the best damn thing to ever happen in the world of drinking and carrying water while out doing things, especially exercising and such. I'm bummed I ever wasted a moment and ounce of energy on any other method, growing up, in the ARMY, and the rest. Canteens, Nalgene, etc, can suck it... rigid pains in the ballsteins.

What are you worried about, exactly? I must've consumed 2000+ hydration bladders worth of water by now, out of only four such bladders in many years, one of which I lost, one I broke, and one I got rid of just to get a bigger one. Literally zero issues with the things themselves, nor have I ever personally seen or heard of a friend say a negative thing about them, and that's after 20 years or so of biking and hiking and such with them, countless friends with them.

Color me surprised/perplexed.