I think there've been some recent changes in PS policy, but I can't imagine they affect Boma. I'd say go ahead and call.
Having said that though, even if they don't take PSs 3.5 months out...mid-September should be a slower time and what with Boma's fast turnover, I bet they could accommodate you even if you make the PSs closer to your dining date. (unless, of course, you have an unusually large party...)