500A on 10s is 18.5Kw, 300A is 11.1Kw. I might be a bit confused where your 2.6Kw number comes from.
I put 4 flights on the shrike today. crazy fast (definately a perspective opinion =)) off a fresh pack. the pulsing issue was a combination of low timing and the low voltage cutoff. I tried re-enabling the LVC on the second flight after the first went great and it started pulsing again although not as severe. I maybe should have taken a hint though as i overheated and puffed the pack so bad that one of the cells melted the heat shrink off along the sides and 3 cells puffed. made it a ***** to get the pack out from the bulkhead it was wedged in. Im planning a new approach using 2 6s1p 1300 packs in parallel. they should fit nicer, give me more amp handling and allow me to lower the amperage to get the same power out of it. i was running a 7x6 before but ill probably have to step down to something like 5x5.5 (according to ecalc). should make for some more high revving fun times and hopefully more reliable as the 5s setup has been nothing but trouble. If im not smoking escs or puffing packs, im breaking motor shafts and props on landing. Makes me glad im using hobbyking equipment going through components like this lol. made me say "holy ****" the first pass i did though!