Hi-flo in OE location is what was called STS
Hi flo w/in 6" of OE is what was called STX
I know the class names are revised for 09--and there were some larger tire allowances in STX FWD/RWD as well (AWD stays at 245s).
STX is the better fit for the heavyish Focus--LSD helps a ton, along with the possibility of wider wheels (8 vs 7.5) and/or tires than STS. The top STX cars are only a smidge faster (on average per PAX/RTP) than the top STS cars--and a STX Focus will easily beat a STS Focus if both are at max prep.
As for DSP--Aaron Williams in Chicago does quite well in his SVT. Its no match for the panzer BMWs--but it'll run with the Hondas and most others. He was mid-pack at Nationals....