I've had a quick look on ebay, what about 2, 2 into 1 collectors followed by 1, 2 into 1 collector, this picture explains it much better:
http://cgi.ebay.co.uk/LOCOST-VINDICA...t _1096wt_939
Im guessing this will use AshG's method, but im not sure if it will be easier to fabricate than a 4 into 1 collector.