Well I went back to my LHS after work last night and pulled the trigger on the GRP .28 promo kit. After I saw it in person on my lunch hour, it ate at me for the rest of the day. I know there has been a lot of debate regarding the .21 vs. .28 in Truggys. I myself have never used a .28, I'm a big Picco fan and have been running the JPX .21 for a while now.
My own reasoning for jumping on the .28 bandwagon came down to (2) things.

1. I have been noticing that certain drivers at the track are finally learning how to harness the power that these .28's are capable of, and it's quite impressive. I think it's like anything new, there is always a learning curve to overcome. The curve exists for the drivers and the manufactures. Drivers are learning to handle the power while manufactures are learning to deliver a more "drivable" powerband while increasing runtimes.

2. When any industry starts to make a shift one way or another its a slow process. I'm sure this comparison has been made a thousand times, but Motocross's Two stroke to four stroke evolution is a classic example. Many riders held out riding their two stroke 250cc as long as possible, but eventually they made the switch. The industry had already shifted and the riders had to adapt. I believe this is the sort of change we will see with the .28 in the Truggy class. More manufactures will start to market their .28s as "Truggy Motors" sponsored drivers will begin run these motors and eventually the .28 will become a standard in the Truggy class.

Once again, this is just my own reasoning, who knows maybe I'll be back to my JPX.21 in a few weeks, maybe this is my own cockamamie excuse to help me feel better about forking out $450 for a new mill, but for now I'm looking forward to breaking in and learning to drive the GRP .28. Just my 255 cents.