adjust the flow of the pump just past the output before the venturi.. sounds like you need to add a valve there. I think that will solve your problem (carefull not to adjust the flow at the input of the pump, it can damage it..)
gate valves are far less sensitive and much easier to adjust then ball valves.. but will cost ya... at least 7 bucks online..
When you say DIY
page... what are you refering to? it does sould like one Ive seen but I dont want to be guessing.. :P
skimmer types I like best (venturi isnt my favorite..)
needlewheel.. (easiest of my favs.) yours could be moded into one of these easy..
becket.. (too big for your needs)
downdraft (can be made small enough for your needs) I like the counter current models with the downdraft tube going strait down through top of the skimmer body..
If I cant find a decent deal on a used skimmer.. I might be building one as well :P