Not convinced hobbling the FXO is the way to go for competitive racing.
The RB4 and XRT are VERY competitive with the FXO, on some tracks, and in some peoples hands, also, tyres come into play.
I was racing with Gener_Al the other night, I was FXO, he was RB4, we were on South city chicane, I was quicker, but struggled to pass after he got infront at the start because of the superior traction, I managed to get past, but towards the end of the race he was closing again because the FXO's tyres had gone off (it was endurance night BTW)
Also, I have had a few occasions on Blackwood where I have been beaten hands down by both the XRT and RB4.
So I would say it's just not as simple as hobbling the FXO, because in the right hands the XRT and RB4 are more than a match for it.