Maybe this will help save your old bad back for the session?
lazypump.JPG [ 462.23 KIB | Viewed 868 times ]
It is to short for my tallest friend, but to tall for the shortest and for me perfect after 3 cuts.
So if you have a old dead pump and some time on your hands start longer and test untill you get what you want.
I also put a nylon over the intake with a plastic pull tie and a one way valve at the nozzle to keep sand out.
Where I fly the wind kicks and sand goes everywhere!