520-92 is stock length and on adding length there is a lil matrix in Dennis Kirk Magazine I hav at home that says how many links to add/subtract when adding length in swinger or adding/subtracing teeth on sprockets so if you dont get that info b4 tomorrow i will post it for you
with my plus 5 we used a 120 link 520 chain.. i think i cut off around 8-9 links.. your best bet is to just get a 120 link and cut it.. its no more expensive then i stock length chain. get a chain brake... or just cut the end of the link of the chain off and hit the round part you just ground off with a punch pushing the link out.