I would like to keep it short and punchy... also, the roads that connect the three sides are not very nice... for instance to go from lake Vyrnwy to Dinas Mawddway one has to take quite a long stretch of the A 458, which is not very nice....
so it look like it will be 50-60 km with 1300 vertical mt... should be 1.3 AAA... according to any tool I have used and my own GPS measurements .
I have seen other 50 km events with 1.3 AAA in the perms, so that should work.
The idea is that I expect people will submit GPX tracks these days... but I will supply info controls for those who don't and a start/finish control in Bala.