Hi Wim - very good to hear from you, now we know where BC26 015 lives!
Sorry to hear that you're having trouble with the mainsail slides, and I'm puzzled by your finding that the steel necked slides are slightly larger than the plastic ones. My recollection is that when I got the new steel ones they were slightly smaller than the plastic, as per spec. I'll have to measure them again next time I go down to the boat. My experience is that when the slides are new with a bit of Sailkote/Maclube on them, in the harbour with no wind, the main drops like a stone straight down onto the boom in about 2 seconds! Over time the Sailkote does build up a bit and gets slightly sticky, and if there's a breeze blowing when you drop the main, then it doesn't take much for something to catch or jam slightly somewhere. I usually find that raising the sail a little when it sticks in combination with pulling the downhaul usually gets it down from the cockpit, but there are still times when I have to go to the mast to persuade it to come down.
I've also modified my lazy jacks, as I found it very difficult to lift the boom with the original layout. I now only have the lines running to the 3 aftmost points on the boom. The idea is to get the line to the back end of the boom running as straight as possible. With a line attached near the gooseneck the pull on the main line is mostly trying to lift the gooseneck end of the boom, so obviously rather difficult. With the new arrangement I find it very easy to lift the back end of the boom by hand and take in the slack on the lazy jacks line. You don't need the mast end lines to stop the sail falling off the boom because the sail is held up by the slides in the mast track, and this arrangement also has fewer lines to get in the way when raising the sail. There is one downside to this however, which is that when you drop the boom before lowering the mast there is more tendency for the boom to want to swing forwards. This needs a bit of controlling but is still easily manageble, and I'm very happy with the system now.
Nick