My suggestion is to not trade US stocks via spreadbetting on any time-frame less than the hourly, any lower and you want the very liquid stocks and ensure to choose ones with low spreads (Usually meaning high liquidity)...
Trading Us stocks on a 2-minute chart via spreadbetting is not going to work.
1. The moves aren't large enough to cover the spread if you are trading back and forth volatility.
2. The spreads are massive, you'd have to get the movements right big time and a loser would be too big due to the spread.
3. US shares on igindex massively fluctuate in spread sizing which sucks.
4. Slipperage will occur.
5. In markets that aren't heavily traded, on igindex its easy for them to widen the spread massively to accomodate for price movements they aren't hedged against, they can't do this for example on the FTSE100 because so many people trade it and they'd lose their customers!
Interactivebrokers.co.uk - Trade the direct market US shares (Real and best execution, real smaller spreads, no funny business).... Look at the average spread for the stocks your trading and keep this in mind and monitor the size of price swings on the 2-minute chart and ensure that the spread won't destroy any profit. This requires margin and $25,000 to day-trade...
If you can't do that and your serious about trading then i recommend moving on from US stocks until you can... I use Igindex to open swing-trades using intra-day setups for entry (only on small spread/highly liquid stocks) and my dad does a similar thing on Interactive brokers and hes execution, price and spread really beats mine... We'll be up 0.30pence for example in the same trade and i'll be breakeven, he'll be exiting for profit.
If you want to day-trade... Learn to trade forex or indices, stocks i find to be generally easier (but less liquid) because they aren't so complicated, there aren't as many reasons and forces for their momvements intra-day, its usually straight forward in a lot of stocks... Where as indices fluctuate with big volatility, i still recommend them though, from my experience i've learnt most from trading them and then when i started day-trading stocks it was extremely easy going
Hope that krap helps