Here is a review I did a year ago. http://www.findmall.com/read.php?66,1340713
It worked fine in three frequency, best data and correlate but I did not try each single frequency. Since only White's coils are V rated, I suspect the 22.5 will be weak if you use it in 22.5 single frequency mode.
I sent a newer 6X8 to Rob and he should be getting it one of these days, maybe he can put it through the single frequency paces down there in sunny Texas.
I might add that the VDI's seemed close enough that I had a good idea what the target was, but being an aftermarket coil, they might be off a couple of numbers from the White's coils. I seldom pay much attention to the VDI's, the deeper the target, the more the variance.