Matt, i saw in Switzerland a hyper 8 with LRP Z.28R Spec 3 and it was EXTREMELY FAST!!!
I HAVE NEVER RUN WITH 21ENGINE BECAUSE I THINK THAT THEY DONT HAVE POWER.
If you check on technical specifications of each engine you will see that Hyper 8port is 2.somethingHP
The LRP is 3.8hp!!!
the thing is that you all recoment 21 engines... OS VSPEC - HYPER 8PORT, no one 28, you know better than me because i dont have any experience.