One thing that is difficult to measure consistently and accurately is pickup shoe tension. Pickup shoe tension is the amount of force that is exerted by the pickup shoe at the point of contact of the track rail. Here's a tool that can be easily made to measure that force and help you to make sure both shoes are equal and that they are not exerting too much force... just enough force to maintain shoe contact but not too much that it encourages a de-slot. If this interests you then read on...
It really doesn't take much just some wood, styrene, screws and 1000 gram digital scale. The scale I got from Harbor Freight, and the rest I picked up from my local hobby shop. I got about $15 dollars in the whole thing.
I glued the two pieces of styrene sheets together to create a two ply deck. I used styrene because for me it's the easiest material to work with... you can use other material if you like... it just has to be solid and does not flex. I cut the three pieces of wood and mounted them to the styrene deck using screws.
I made the deck and the wood so that it was a close fit to the scale. This way I could slide the scale under the deck all the way until the end piece of wood stopped the scale. This would ensure that the scale was always positioned the same every time.
I then made a little plunger that went through the hole in the deck and made contact with the scale itself. It is made of styrene also. I used a body screw and screwed it into the top of the plunger. Now that screw is very important. It is adjustable so that you can adjust the height to match the height of the track rails when measuring the shoe tension.
Below is an example of how you can rest the shoe on top of the plunger.
The shoe will push down on the plunger and it will push the scale down and it will measure in grams the downward force the shoe is exerting.
This set up allows you to measure consistently the same way every time.