im going thru a similar prob, , im restricting my nc30, i was gunna go my own way and buy the washers fit them myself get a dyno to prove the restriction, how ever the benefits of going the rip off FI international way is that the snogs are not likley to pull you over if you go this route, IE..
you go past a ANPR car and they take your plate, you flag up as owning the 400/600+ bike but your on a restricted llicense, your gunna get pulled...
The FI way your bike is logged thru the dvla and vosa as having a cert of restriction, the bikes in your name the certs in your name, insrance is noted in the mods as being 33bhb, if it all adds up your likley to not get pulled as the papaer work adds up ok, and cops hate paperwork im told unless your riding is aggresive and so on.
you could go the cheap way and do it your self but i think you will get a lot more hassle from the coppers , and once stopped they will be all over your bike like a rash , tyre treads , pipe too loud , plate to small , visor is to dark etc etc
by this time you'll be fed up with the 10th pull in a week and be arrested for public disorder (i would anyway)
ok the point being you need not have any proof really other than YOU know its 33bhp and within the limits of the law , but hassle wise id go FI way, i was tempted to pull out the restriction but a solicitor i know who is a friend and biker, said if you were gunna do that and were to cause a death in a accident you will be lookin at 6 year min prison sentence,as there throwing the book at you for this now he also said that a lot of insurers are droppin the restricted license holders purley for that reason there pulling out the restriction on there bikes and dying, he then went on about there trying to drop the current system of a1 licences and soon you will have to do a test on a 400 then again on a 600 and work your way up,(not sure if this is true tho )
sorry about the rant but its a catch 22 situation here your damned if you do your f**ked if you dont
