thanks for the good info guys - just for my own peace of mind I tried a totaly different "extreme" set-up to see if I wasn't going off the rails - blue springs up front - white on rear, no roll bar - and all other things equal - I reckon the steering off power was probably better! Back to the drawing board
Anyway this aside - during the heat of battle a fellow racer gave me a love tap sending me skywards - (the russian judge only gave me an 8.5) when I landed the car pulled violently to the right on power and to the left off power. I had clean snapped a drive shaft. Never seen anything like it. Was I just very unlucky - probably - I can't believe XRay have "bad batches" ! So running a spool can have other disadvantages. The power had nowhere to go except to take the drive shaft past its elastic limit and then some!