I have and still use the 810SL on my 35. It's often hard to furl in a blow. The most important adjustment you can make is to ensure that the outer casing of the the lower section does not rub against the upper casing. If they rub just a little, it can really increase the friction. Secondarily, the rotational orientation of the lower casing must be just about perfect to ensure that the furling lines do not rub on anything - particularly when under load and furling IN. Both of these adjustments should be checked under load (at a dock with a modest breeze).
The lower section is adjusted with an allen screw and both clearance to the upper casing, and orientation are adjusted at the same time. I remove my furling line each year when I drop the mast, so I have made a mark so I can get it back together the same way each year.
On my unit, either the upper or lower casing is a little cockeyed, and I need to have a 1/8-3/16 clearance to ensure they don't rub while under load. If you have them too far apart, the plastic stripper might fall out, and the furling line stands a chance of getting caught in the gap.
Having said all that, I would like to some day replace it with a single line furler that I can safely use to reduce sail. Hood sells a single line replacement unit, but I've never been convinced it will fit below deck (which is sort of nice). Harken now has some nice below deck units, but it still looks like a big project to retrofit for one of those.
Chris