Finally got around to building a test 2Pac with good chips and ran a quick efficiency test, only up to 300MHz because my USB power meter is only rated for 3A.

Freq	GH	Vcore	Power	J/GH
100	11.00	1.26	3.67	0.33
125	13.75	1.26	4.48	0.33
150	16.50	1.26	5.27	0.32
175	19.25	1.26	6.12	0.32
200	22.00	1.32	7.43	0.34
225	24.75	1.36	8.73	0.35
250	27.50	1.40	10.11	0.37
275	30.25	1.46	12.25	0.40
300	33.00	1.50	13.98	0.42

At 300MHz, the total device efficiency is only about 15% worse than the datasheet chip-level efficiency, which I think is pretty good for a stick miner. It also puts up over 30GH, which I think is pretty darn good for a stickminer. Note this is about the same power draw the original Compac expected to see at 22GH, so we're seeing a 50% improvement in hashrate. If the stick could be pushed to 400MHz you'd see it drawing about 23W for 44GH, but I don't want to test this until I have a bit stouter measurement tool.

I'll copy this table into the OP for reference.