Wengier,
Hate to sound thankless, but I think something has happened to the speed and responsiveness
of the most recent vdos-lfn/vdosplus versions, June 2016 vdos build. Unfortunately, I can't date it to a particular recent version.
The only older version I've retained for comparison is vdosxy3. The easiest test is paging backwards through a long document, holding down the "previous page" command, so that its repeats. The difference likely won't ruin anyone's life, but vdosxy3 is at least twice as fast (with xy3). Could be I'm mistaken, but I don't believe this was always the case(?)