thanks for the info on Koppert lake. That's looking my best possibility at the moment as I'm spending a few days in Portland with a friend who has agreed to go there with me (she will be trying out wakeboarding for the first time!) so thanks for suggesting it. I wouldn't have known it was there otherwise.
Anthony, I haven't sorted out what I'm doing in MA yet, but staying with a friend with young kids and a baby, so less likely to be able to get her to take me wakeboarding for a day
but if it looks like I'm going to have a spare day and some way of heading north, I'll email. Thanks!!!