A smaller futures contract than YM/ES is ideally DIA & SPY futures.
( 1 contract=100 shares & 15-20% margin I think at IB)
But the quotes can be very wide & no quote some times.
If you have enough funds then instead of trading DIA & SPY ,trade DDM /SSO. ( SPY=145: SSO=86.50 approximate)
Lower investment (60% SPY) & almost 1.5 times leverage.
BUt all utra spiders usually quote 0.05-0.08 spread unlike SPY/DIA whcih is 0.01 always.
I love UWM instead of IWM & QLD which is Ultra QQQQ.
One fact - Long ultra spiders have low daily volume (200k-700k) where as short ultra spiders SDS,DOG,TWM,QID trade average 800k-1 million and above.