My Catalina 250 had a similar one-line system. I found that putting a block at the aft cringle greatly reduced the friction at the very spot where it was needed. The block had a shackle that reached through to a ring on the other side.On my last boat, I had two line slab reefing. It worked fine, but I wanted to "upgrade" to a one line system. It was a relatively small boat (O'day 23), so all of the lines ran outside the boom, making the project an easy one. To my surprise, the system didn't work as smoothly as I thought it would. Because of friction, I often had to give a yank on the reefing line at the clew to bring the aft end of the sail down to the boom. I thought this was probably because of the design and position of the blocks I put in rather than a systemic problem. In short, my own fault. In retrospect, I now think differently.
When I bought my "new" boat, it too had a one line reefing system. On this larger boat (Catalina 28), the reefing line runs through the boom (just like a big-boy boat). I was initially surprised to find that I have to do the same thing at the clew with this boat: the friction in the system requires help for the clew to be tensioned. That means giving the line at the aft reef point a good, hard yank down in order to get enough slack in the line to pull the line through the boom. Just too much friction.
I'm going to see if there is a way to make this easier; if not, I may just revert to a two line system. I'd leave the tack end the way it is, with the line leading back to the cockpit. But I may just install a new cheek block and cleat on the aft end of the boom to handle the clew.
I then tried a similar block at the tack, but it caused more harm than good. In order to get sufficient clew tension, the tack grommet would pull below the boom and ruin sail shape. Jockeying halyard tension to compensate while underway was more hassle than I wanted. Just running reefing line through that cringle forces it down to (not below) the boom, then I can get going without worrying and adjust halyard tension independently.
I’ve been meaning to modify my current Catalina 34 in the same way, but having difficulty finding a big enough block that doesn’t cost a fortune. I stop by the consignment shop periodically.