OK - I finally did it and ordered a 80mm stem - not too expensive and 10g lighter than my Specialized Pro-set that came on the bike. I figured I needed around a 15 degree angle to keep the bar height the same (current angle is 10 but the new stem has less reach). However the new stem has only 5 degrees, but I have 2cm of spacers under the bars, I figure I'll have to swap over 1.5cm in spacers and then I'll be about right. I can play with that as well.

Reports will come after the parts arrive and I get a chance to try things out.