I have been using foam jump cups for the summer in my practice groups. I believe they answer concerns about the safety of jump-cups and they are easy to install, quickly adjusted for heights, and I made enough for 18 jumps for $3.00!
I bought a couple of swimming noodles from a dollar store, cut them in 2.5" segments, put a slit on one side and used a Dremel tool to for a slight depression in the foam opposite the slit. All of this is shown below in the photos.
After a summer of using them, I can report that I have not heard any negatives about their use. I use them on jump standards made of 1" PVC, with marks on the PVC for aligning the top of the foam for the different heights. For 4" jump bars, I have needed to use my old plastic cups because there isn't room to place the foam below 4-inches, but the foam can still provide some safety by pushing it down to a couple of inches above the bar.
The only drawback that I have seen is that they need to be removed from the jump standards at the end of the day because leaving them on will cause them to loosen their hold on the PVC and will slide with the weight of the jump-bar the next time they are used. After they have been removed for about 6 hours, their elasticity will return them to original diameter and they can be confidently used the next day.
I will soon be going into the winter season in an unheated barn. If anyone is interested, I'll be happy to report how well they do in the cold.
Even if I have to make a new set every year, $3.00 is far less than what I have to pay to replace the few plastic cups that break throughout the year.
I may not be the only one who has thought of this, but I'm happy to share with anyone who is looking for inexpensive and safe jump bar "cups".
Lynn
