I stuck my nose in there once, but turned back and went to Cuttyhunk - and that was in my old Morgan 24 with the centerboard. I've been there since on 2 wheels, and there's quite a bit of room. Kinda like going into the harbor of refuge at Sandwich, MA.
A friend took his Alberg 23 all the way up into the Pond, but I consider him a bit more adventuresome then me. He brought the same boat from Detroit via the Erie Canal to CT.
Hey, it took me years to finally poke into Tashmoo.
It's funny - you look at these places on a chart, and you get no sense for how big or small they are. I think some of the electronic charting software will show a scale sized boat on the chart - helpful feature (for me). I know, I look at my marina on a chart and think there's no way I'd go in there - but I do, frequently. There's a rock in the entry that I've learned to avoid at low tide (not on the chart), and my slip lets my keel into the mud about 6" at low tide. One day I actually had to lasso a dock cleat and use a winch to pull myself back into my slip, but that was a neap low.