I measured the "amp-enable-to-RF out" delay on an IC-706MKIIG at about 12ms, and on an IC-7000 at about 8-10ms. I'm guessing that the '756P2 is in that ballpark as well. The open-frame relays in non-QSK amps take typically 15ms as you've discovered, and Icom doesn't provide an adjustable delay. You might want to take a look at the relay-based QSK mod I did on my ALS-600 (info in the "Equipment Modifications" section of my website at www.ad5x.com
). This improves amplifier switching time to 3-5ms.
But then with faster switching you need to worry about whether the '756P2 unkeys the amp before RF has completely gone away (a problem if you operate QSK - not when operating semi break-in). I know this can be a problem in the IC-706MKIIG, the IC-7000 and the IC-7600 - but don't know about the '756P2. I have an article on how I solved this (ALS-600 Flexible QSK Keying Interface) in that same "Equipment Modifications" section of my website.
Phil - AD5X