Nottingham Horizon SE

I've acquired a Nottingham Horizon SE TT w/modified RB300 tonearm (Incognito Rewire & Origin LIve Structural Mod). I'm getting to know the TT and have some questions: 1) The RB300 sits in a custom collar on the armboard with two small Allen screws that tighten the armbase in place and allows for VTA adjustment. There is NO large pipe nut underneath. Is the large nut even needed to properly seat the tonearm? If so, does it interact with the RB300 collar? Are there +/- effects on the fidelity with the use of these tightening devices? 2) There are a gazillion known tweaks for the RB300, are they any for the Nottie? 3) Who services or carries this product in the US? Any input, suggestions, personal experiences would be helpful. Thanks!