Ben - Thanks so much for trying this and laying it out.... I was thinking of using a longer bottle with the Speedfill bottlle lid. I thought this approach would help elongate the top part of the bottle and keep the lid and straw essentially tucked between the area of your arms and "top" surface of the bottle. This would also be a great place to store a couple gels...

Part of me is wondering if there is a way to make a cage / cage holder (3d printed) that acts like a fairing to clean up the transition between the bottle sides and the arm rests...

Its got me thinking! Thanks again!!

Cheers
Mike