5x7" tanks are cheap and plentiful. You can get older style hard rubber ones on eBay or look for a used set of stainless tanks (try finding them locally on sources like Craigslist, because they can be heavy to ship, particularly if they come with a water jacket), or buy new ones with floating lids--

http://www.bhphotovideo.com/c/produc...allon_5_x.html

If you get older hard rubber tanks, buy more than you think you need. Some have hidden cracks, which can be sealed, but since they're easy enough to find, you might as well use the leaky ones as dry tanks for storing hangers and holding them temporarily while you load before moving them to the developer.

Bromide drag around the edges of the frame is usually caused by insufficient agitation.

I process sheet film using open trays, daylight Nikor sheet film tanks, and with open tanks and hangers, and when I have a lot of film to process, tanks and hangers are the most efficient method.