RE: need advice on a slalom board
my estimation: modern 75 liter slalom board or a bit less, eight feet or less. If you could accept 6.3 as your biggest sail you could get a smaller board and have a more comfortable ride on the 4.8 days. Other factors would also dictate, like % of time you expect to be on the smaller vs bigger sails, how gusty at your spot... etc. However, looking at the isonic 50's specs it can handle a 6.6 and at your weight, maybe would work well with the 6.6. Although the is50 might be more of a speed than slalom board. The 2007 jp slalom board at 69 liters might also be worth taking a look at. I tried it with a 6.0 which it handled with no problem. I was surprised at how big it felt for it's size.