Hi Jon, have you tried immersing the ends of the hose in hot water
for 5 minutes, and putting dish washing
liquid on the loop before pushing the hose on? That worked for me when I replumbed the head in my boat
. If that fails, is it possible to dismount the vented loop, install the hoses when it's in a better position, and then remount? I know some hoses have a bit more stretch than others - usually in the specs they'll say the minimum radius turn it can handle, which gives you an idea of he stiff it is compared to a different hose type.
Hope that helps - I know that wrestling with that hose isn't a lot of fun.