Hi Mike
My background is mostly Flying Duthcmans, I started sailing at 12 (in FJ at first) and sailed for about 10 years before coming to Australia, over the last 20 years I have done some more sailing in Perth.
I have been sailing and racing my Tattoo for about 12 months, in Division 5, competing against Court 650 and 750, Sorcerer, MB21, Endeavour 24 and Beneteau F235, H28 and some spacesailer 27.
As the knowledge of this unusual boat started to improve and got to know the sailing conditions in the area I started to have reasonable results.
So far I got a 1st, 4th and a few middle of the pack results out of an average of 12-15 boats per regatta.
The best conditions are in about 9-12kn with a genoa.
The club has given me an appropriate handicap and it gets adjusted every few races.
When I eventually get better sails (proper racing sails that don't go baggy) I expect even better results.
I have not bothered answering ANY of the various blogs that are bagging the Macgregor, but as far as I am concerned most of them are all talk and no substance. Most of them have not sailed in a Mac (or can't sail)

.
Having said that, you will be at a major disadvantage once the wind gets to 15kn and above and expect to come just about last but still have plenty of fun. At 27kn I stopped having fun
Before I forget....The National Yachting Federation handicap for the Mac 26/Tattoo is : CBH .715
for the X : CBH .665
For club races it gets adjusted after a few races, mine for the Tattoo is around 0.38 with the rest of the fleet at about 0.4425 to 0.5135
I hope this helps
Have fun