Thanks all for replies!
Please rest; I was a guest at the wedding.
As the family member I had the opportunity to try my new Sinarback 54M, which I bought for my studio work.
I set Contax 645 and flash to f5.6 and ISO 100, which provided approx 10 meters of working distance in low light. The Macbook was in shoulder bag, this added mobility. I think the Sinarback 54M was able to capture images each 2-3 seconds.
I encountered a number of problems. Macbook with a spare battery adds significant weight. Focus in C645 is slower than Nikon and may fall in low contrast.
CaptureShop may crash after Macbook goes to sleep. When Macbook wakes up a Relaunch dialog is shown. I forgot to set Macbook to Performance mode, as Thierry recommended, to minimize sleeps. I will test shooting in Performance mode with batteries again. Also Macbook may crash. I don't know if setting Performance mode will help.
Folks, that's all for now
I have to do more tests.
The 54M captures images of fantastic quality, especially compared to DSLR.
Thanks