Update:

I'm starting to think my '--set-device antminer:freq=0981' command in BFG Miner isn't working properly.  Before I was looking at an average hash rate of 5.5 Gh/s with that setting with BFG Miner. 

After trying the CG Miner provided by BitMain I reverted the drivers back to the regular ones to use the U1's with BFG Miner.  After using the same .bat file with the above freq command I'm now getting more HW errors but a faster speed similar to what I would expect the U1's to do at 2 Gh/s. 

 Block: ...3b2c1f04 #280440  Diff:1.79G (12.81Ph/s)  Started: [11:13:50]
 ST:15  F:0  NB:2  AS:1  BW:[ 69/ 61 B/s]  E:28.05  I:90.22uBTC/hr  BS:1.25k
 4             |  8.22/ 8.18/ 7.59Gh/s | A:328 R:1+1(.50%) HW:112/8.7%
--------------------------------------------------------------------------------
 ANT 0 :       |  2.06/ 2.05/ 1.70Gh/s | A: 87 R:0+0(none) HW: 46/ 15%
 ANT 1 :       |  2.07/ 2.04/ 2.15Gh/s | A: 78 R:0+0(none) HW:  8/2.4%
 ANT 2 :       |  2.07/ 2.05/ 1.71Gh/s | A: 68 R:1+0(1.6%) HW: 21/7.3%
 ANT 3 :       |  2.06/ 2.04/ 2.00Gh/s | A: 95 R:0+1(.58%) HW: 38/ 11%
--------------------------------------------------------------------------------

My procedure was to uninstall the WinUSB drivers after using the U1's with CG Miner and 'rescan for hardware changes' in the device manager without unplugging and replugging the U1's again. 

After that I ran my BFG Miner bat file.  If I'm right, setting the freq using CG Miner and the WinUSB drivers would properly set the overclock on the U1's but the BFG Miner command doesn't seem to work - for me at least.

A bit more testing is needed but at least I'm getting somewhere.