Frame bag chain ring clearance necessary?

[Wilburforce]

Hello there,
I was curious about chain ring clearance - I use an internal gear hub or SS so there's no front mech to worry about.

Nor would it be a problem for the velcro as I will be using a webbing ladder with One Wrap velcro wherever I deemed it appropriate - like this - https://www.alpkit.com/products/possum

But as it's a large traditional road frame - would it be a problem with a 2.5-3" or 6-7cm wide frame bag to go to the bottom of the triangle..?

Obviously at those widths the bag doesn't overlap the BB shell. But without actually stuffing things in a completed bag I can't tell whether I should be prudent and end it a cm above the chain or just go to the bottom...?

Thus is there generally a consensus on chain ring clearance - likewise am I just inviting muck or water to congregate and seep into the bag if I go right into the corner?

Thanks

[Smo]

An easy solution to the clearance issue is just to taper the bag near the bottom.  Just make the seat tube and down tube panels get a little skinnier for the bottom few inches. That's what I did on the framebag in my avatar, which I wanted to have fill the frame completely for aesthetic reasons.  It was a 2.5" wide bag in general, and i tapered down to 2" - it's just enough to clear my derailleur and works great.