Yes, 55 is going well. Have sailed it three different times over the last two days. First time for a late afternoon sail yesterday at the West Inlet (my first go on the sand bar). Sailed it with my MACH2 6.2 and a 23cm Tribal Weedspeed (didn't have my trailer and forgot my main fin - a 23cm Slingshot)! Wind was up and down, but the board felt great. Easy to get on the plane, gybed really well and felt good off the wind. Managed a 40 knot run, so all good.
This morning sailed the same spot with the same sail and fin. Wind was a good direction for a few runs, but then went more broad and strengthened. Top 2-second was a 41 knot run, but the board (and rig) felt a bit big for the conditions once the wind picked up (quite choppy in the lead-up to and then at the end of the run).
Drove 5hrs back south and went out again this afternoon on the 55 with the 23cm Tribal weedspeed at Dorans, but this time with my MACH2 5.5 as it was howling, bump-n-jump conditions. Board felt great.
First impressions are that it is easy to sail and sensational for gybing, as the gybes I did, although not within the alpha 500, were fast and controlled. Super easy to do 40 knots and will no doubt go quicker with a bit more tuning and a better fin, as I did spin out quite a few times in chop heading into the run, which made me a little hesistant to go full-speed into the run.
Cookie was sailing with me both times at West Inlet and had identical gear, except for the fins and got similar speeds and enjoyed the board.