I used to own a Pro Sport with a thrust bearing between rear guide and trigger block. The guide was custom made to accept one half of the bearing, the other half was set in the trigger block. This was a roller bearing consisting of three parts if I remember correctly.
I too did not notice any difference in accuracy. It was still running the full 98mm stroke and was very hold sensitive.
Challenge HFT .177 16J | Optisan 10x44 | HW50S .22 16J | Fomei 4x32 | HW95K .177 LB 16J | Valiant 4x32 | HW80K .22 LB 26J | Valiant 4x32 | HW97K .177 16J | Schmidt & Bender 10x42