I have the 65 litre Blast. About 20 (?) sessions on it now. My first sub 85-litre board, I am 81 kgs. Intermediate but ambitious wingfoiler. I also have a 90 litre custom mid length, so nice combo.
Apart from very light conditions or when I need to go a bit to get out to the wind line (or back), I almost exclusively use the Blast 65. I run it with Axis ART V2s, 999 and 879. With the 999 and my 5.5 wing, I'd say that I get going in about 12 knots, maybe a bit less. The take-off is actually not that far off from my 90 litre mid, I was expecting a bigger difference. Really like the board, light, good construction (it is different from the previous red Axis wing boards, other factory?).
I was a bit hesitant about the size, but now think that it is perfect. I can schlog back if needed, and it feel nice an nimble when riding on it. Unfortunately, I cannot compare it with so many other boards in the same size since I have only tried a couple. But, I think that the length, width and overall shape is spot on for my needs.