There is a way, but you won’t get an exact 7.5" length out of the combination. You could put a pair of HUB-08 back to back and attach tubing to each end. As I said, this will not get you exactly 7.5" length though as it will be just a bit longer. The only other way I know of to get exactly 7.5" is to cut a custom length of tubing.
Part#: 9924K171
Alloy 6061, Hard T6
Military Spec Aluminum Tubing 1/2" OD, .430" ID, .035" Wall, 3’ Length
In Stock at $13.05 Each
Part#: 9924K172
Alloy 6061, Hard T6
Military Spec Aluminum Tubing 1/2" OD, .430" ID, .035" Wall, 6’ Length
In stock at $25.10 Each
This is the same tubing as offered by Lynx motion, but without the the know how and work done. Cutting the tubing straight is not hard, but drilling the holes and getting them right is where the patience comes in.