I spent some more time on it today. I consider it to be finished.

1. The pressure gauge is now mounted nicely and firmly in a place that
is unlikely to be affected by load, chains and other forklift use.

2. I figured out how to deal with errors caused by friction. It is
very simple. I just need to take two readings, one after creeping the
load up, and the other after creeping the load down. The average
cancels friction out. Problem solved.

4. I lifted another forklift on the forks of this forklift, took down
pressures, and I now have a nice and easy conversion table, PSI to lbs.

5. I realized that maximum pressure in the system is always well under
2,000 PSI (20,000 PSI would occur only if this 15k forklift tried to
lift a 20k load). So, my oil filled 5,000 PSI gauge would have a great
cushion against pressure spikes.

6. Everything is neat and tidy, the pressure lines do not rub against
anything, the gauge is easily visible, yet protected, etc.

I will probably put similar gauges on all my forklifts.

i