Flip FPV (long arm rebuild)

Ok this is where I'm at with this frame...
I did 4 arduous tuning sessions with the small arm setup (without a bluetooth, not advisable...). I got close to a smooth hover in rate but in forward flight it behaved like it was under fire from a battery of flakk guns...
I'm not the most methodical tuner by any means but I know what has worked in the past and I couldnt get it near the sweet spot in forward flight. I'm sure it can be done, I just dont have the time as I leave on a multi country trip in 5 days and need something that will fly well now to take with me.
So I went to plan b for now - swopped out the spacers and chucked on an old set of 450 arms (the centre plates take both types of arms fine).
Guessed some pretty basic settings and got it flying fairly well in 5 minutes. It needs some tweaking for sure but I'm not a patient tuner so I just took it to work, pulled over at a spot I knew and gave it a thrashing...
Why it flies better when the long arms make it even less symmetrical, someone with a bigger brain than me can answer, but it definitely seems to. So although I loved the indestructible feel of the small arms, I think I have to stick with this setup until I get back in a month and have the time to really tackle it properly.
Info on the frame and build is here: