Have you seen camlifter's 2 stroke V twin motor?We are in the process of putting together a new Grubee V-Twin and buliding a nostalgic bike.
K just saying personal opinion.... Brazed frames went out many years ago in favor of the stronger welds that can be had with a MIG or TIG. I just am too old to recuperate easily from the injuries a broken frame could cause.
I think it'll be okay. Of course this, too, is just a personal opinion, I admit. But I took a long look at the picture. If the tubes are as thick as he says, well, it is a partially lugged frame - bottom bracket all points, head tube both points, seat post at top tube and at bottom bracket. My only area of concern would be the seat stays and, if there's a cross-member behind the seat post like it looks like in the pic, he should be alright. That's some heavy lugging even if it is just brazed.