With gravity-feed hot water, the weakest link in the system is the shower. Twist the know that 1/64" too far and suddenly the cold water is pushing its way up the hot pipe. Not an ideal way to have a shower.
I noticed that the bath tub outlet didn't appear to be so restricted, so I connected a $15.00 washing machine drain hose to the spout and then slung it up over the wall into the shower recess.
The yellow "shower head" is my flat-mate's addition. It started out life as a pressure canister on a super-soaker. Stabbing a few holes into it with a soldering iron created a nice low-pressure head. The fringe along the top is where heated pliers were repeatedly used to press and tighten until the head sealed with the hose.
I ain't pretty, but it works, and we can all have decent showers at last!