If your Sakurai is a 650mm scale then most likely the lower bout is 370mm. I think you'll find a 1a is slightly larger.
I have a Sakurai 640mm scale and the lower bout is slightly smaller than the norm. I personally spent way too much time going over the Proii/ Artist, size question. In the end I decided I preferred the extra padding of the Artist and the fit just seemed better, overall for the size of my guitar, however, I hated that it cost so much more
. In any event, I originally decided to pay up ( for a couple reasons, 1) my guitar was expensive, and 2) in the long run, I wouldn't miss that money as much as I would be bugged not buying what I wanted the first time around)
My decision was to be...wait for a "sale" on the Artist case and get the one that was a better fit. ( on paper the Artist fit better, than the Pro-ii, not too big, not too small, just right. Met the pad but didn't squish it. IIRC. Squishing the pad too much would defeat some of the purpose in my mind).
However, in the end I ended up getting a custom made case for free, so, thats my anticlimactic ending.