The RB5 is a great chassis and is very forgiving and easy to drive in low grip. Pop over to the Kyosho section of this forum and we'll all be happy to help you fine tune your set-up.
As far as I am concerned the RB5 is the best 2wd chassis I have ever driven and as I started racing in the mid 80s I've driven a few
As for the brushless set-up you have gone for exactly what I would have suggested other than I don't think the PRO speedo is necessary, the LPF would be more than enough in a 2wd car. That said the PRO speedo is great it's just that you won't be using anywhere near it's ultimate capability so you could save a bit of money buying the LPF!