Hey HBJ -
The easiest solution is to queue up an RPi or two and run them separately. I've had terrible results running U3's with anything else - specifically because the U3's have the tendency to go ZOMBIE after not too long a hash. This is pretty well documented on BCT that the U3's were a device Bitmain would rather forget about. That said - let me clue you in on a little secret...
Bitmain just released a small device called the AntRouter. Get one. You can find them at CrazyGuy's website asicpuppy.com and order one with the custom firmware. The AntRouter runs the U3's from what I have seen, very well (much better than anything else. Plus, it's also a wireless router and has a mining chip in it also for an extra few GH's on it's own. I bought one and have been running it for a few weeks at home (for fun) and I'm waiting for a U3 myself to try that out given the results other have had running U3's off the router.
As a matter of principle, I don't mix miners on the same host because it unnecessarily complicates things and is usually less-stable than it needs to be. I have two RPi's sitting around for just the purpose of getting miners up and running quickly and for extra interesting projects around the house.
Maybe this isn't the answer you're looking for (spending a few bucks) - but it will save you hours and hours of frustration in the long-ish run. You'll be happier for it.