Maybe I asked this before - but does anyone have a good recipe for quince paste, as in Spain/Portugal/Brazil, but made with the fruit from a japonica bush?

I have tried before and gotten stuff I like but no one else did, because it wasn't sweet enough. Where we live the japonicas don't really get ripe, but this year as with everything else, we have a bumper crop. I have japonica jelly left over from last year so want to do something different. Do I just need to add more sugar to the standard recipe?