[Graham]

making entrants put their name on the bottom of car chassis ( engraved . sharpie or sticker ) should remove any problem with duplicates 
whether it be team name . forum name . or RL name
  
1st US proxy i entered . i forgot this requirement and received a penalty 

tape or blue tack over screws is a standard requirement for most of the US proxies . so should definitely be employed here 

some also ask for body / pod screw tightening info on the bottom of the chassis 
bit OTT imo . but if tape or blue tack are employed . repositioning of screws should be discouraged during the series . and the cars should be ran as they arrive unless it is obvious the screws are fully unwound or missing  

no duplicate car numbers is a big thing over the pond also . 
dunno why . 
not a biggie unless you intend to run a manufactured tampo livery . stickie roundels temporarily fix this if entrants want to return their cars to stock 

also representing cars as how a 1-1 liveried car should look (even if it is a fantasy livery) in the class they are intended to compete in is heavily enforced . if it doesn't look the part it can be DQ'd

almost all of the above i have found myself in hot water for at one time or another
and never once an intentional breach
so easy to overlook the simple stuff when entering 

Kev

Many thanks for that insight Kev, I do insist that entrants write their name on the chassis and I also use a sticker ID system. So mostly we have this covered. But it is a thought that “in the heat of the moment”   Hosts can still perhaps be confused by identically visual cars especially if they are run side by side. So I think it might be a good idea to ask the entrants to apply different decal numbers if we get into duplicate cars which I can see is more likely with the type of Event 4 GT3 cars. 

I will insist this time around that cars are declared by the Registration date which is about a month before the date of receiving the cars. So that any anomalies like this can be resolved before the cars are sent. Obviously those who send their cars in first will be able to retain the numbers they have on their cars. Any late declarations will get a penalty, as will any cars arriving after the delivery date.