It definately made the solder flow better. I tried with and without... especially when i was trying to remelt the solder for the large battery pads, it wasn't seeming to melt, and added a bit of flux, and it worked much better.
I was stoked to see my post (or at least a reply of my post) with the issue i was having with the FC in your video this morning (missed the live, but watched the vod). Really looking forward to using the builder.