DI and naturally aspirated combo is nice, but a DI combo and forced induction would be even better.
You get to run alot more compression, with the same amount of octane, and since you have a more equal spread over the combustion area to utilize the cooling property of fuel you get even more bang for the buck. Go ask Ford how they can make 350HP with a 3.5 DI Econoboost V6 that has 2 small turbo's, in the SHO 10.2:1 compression. Non DI combo would be asking for issues.
As someone mentioned before, the issue is getting fuel delivery, im sure the same will be the same on sleds as they are with automakers and people who are modfiying direct injection systems. Injectors, and fuel pumps have no overhead, and aftermarket supply is close to zero, even with the demand/supply, its a such a new technology the price is crazy.
It would be interesting to see what the difference is in compression numbers vs a 800r and 800 ETEC. That is where the power gain will come from.