Stu – I think that’s why Eric at Revelate does a long thin dry bag so that it doesn’t get in the way of the front wheel. I’ll measure it when I get a home/back from here and see if I can find an alternative that’s similar off the peg in the UK.
I’m sure from my sea kayaking days I can/could find an alternative longer, thin one – I know there used to be tapered dry bag for getting right into the bows of sea boats.
I have an Alpkit tent bag with straps around too – we’ll see how that does on the bars too.
EDIT – FROM REVELATEDESIGNS.COM
ATACAMA DRY BAG
The first dry bag out there designed for handle bar mounting
6″ diameter fits nice and tight under your handle bars with lots of tire clearance
Lightweight urethane coated ripstop fabric with waterproof, RF welded seams and a minimalist buckle closure.
Use it with either the sling, harness, or take it backpacking.
Weight:3.5 oz
Volume: Approx 12 L Max