i would assume that the extra hole is to overcome lumpy idle ?
an 800cc spray pattern would be pretty narrow, and you'd get less atomisation and so it'll be more lumpy lower down the rev range, adding the second hole gets you two 400cc holes, which is closer to a stock spray pattern ...
however, this is just my idea, and could well be wrong ...
hks v sard - either, i'd have no probs using either
and yeah, you just tell the pfc the correct values in injector setup ... nothing too complicated, you'd need a tune post install tho ..
cheers