I agree - looks like setup B:

If you have two riveted loops on the boom for the mainsheet to attach to then I'd move the ratchet to the boom, attach the round double block to the rear of the two and the ratchet to the forward of the two.
Kinda like this one but only using two of the points at the rear:


I have a separate rope for my mainsheet and traveller on my Taipan 4.9 and just tie them together using a double sheet bend. Works well because I can have a smaller rope for the traveller as well to reduce friction etc.
Double sheet bend tying instructions

Yachting Australia has a list of clubs where Paper Tigers are sailed in South Aus. Go to their site and click on 'clubs and classes' and do a search for Paper Tiger Catamaran in South Australia. Can't link to search results page so here is the site link:
Yachting Australia
Adelaide Sailing Club is one of them.

Hope this helps!