Did you ever find the solution to your dryer vent problem??
There are a couple good products on the market, you can find them at http://www.airmasterfan.com/products/blowers/Catolog/Turbo.pdf, or http://www.acmemiami.com/dryerjet.html#dryerjet.
The first one is harder to find Ė it used to be sold at Home Depot, and may still be a special order item. You must order the pressure switch separately, and need be installed half way up your line and wired into a power line. AirMaster is not very responsive, nor are their distributors, as they are focused on the major markets, and donít seem to care much about consumer market.
The second on is a small company in Florida, and their product can be installed by the dryer, and plugged in to a standard outlet. It has the pressure switch built in, to make operation automatic.