I just converted my Electra jet to brushless direct drive this week.
Mega 16/15/8 using 9.6 Hecell 1000ma packs. Speed picked up 50% but duration increased by better than 75%. 6 mins. of great performance with 2 mins left to tool around and another min to set up the landing. I belive there my might be a little more to be had as i am rotating 3 new packs thru the bird and they each only have around 4 flights and it takes a several cycles to get these packs up to full capacity. My last flite today with a warm pack was at a tick over 10 mins but there wasn't any left for a go around. The best i could do with 600AE's and the gear box was around 4 1/2 to 5 1/2 mins., tops, and the last couple of minites was lackluster performance.
I want to try a 9 and a ten cell pack and will report back.
I might have gotten a mega with less turns but I was concerned with the duration. But I think i can trade a couple of mins to pickup some more performance.
I also removed the bottom skid and epoxied a 3/16 dia. wood dowel from front to back along the bottom to put back in the rigidity. The plane performs better (to me) without the foam skid, especially in a dive, I felt the skid was acting like an airbrake. plus now the plane slides a little when it lands rather than burrowing the nose with the skid in place.
I read some other post that guys were having some handling problems. This thing needs no more than 1/4 inch up/down elevator throw to do anything that needs to be done and will fly well on less. More elevator will only make it way too responsive.
On the other hand, run as much airelon as you are comfortable with
Always launch into wind, otherwise it will nose in. If there is no wind then give it several clicks of up elevator trim before you launch, then once its up on step you can trim it back level. Taking some elses advice i programmed in some up trim on my landing switch and click it on just before launch and then off after gaining a few feet of altitude. What damage i have done to mine has been nose in launchs.

take care
z123