UIM · Hull and handling
Only the GP1 classes have a ballast article - and they are the ones with the lowest weight minima.
This matters commercially: GP2 Runabout carries the heaviest minimum in the book at 310 kg and has NO ballast permission, while GP1 carries 300 kg and may ballast up to it.
24 classes, grouped by the answer rather than listed one by one, because an answer that holds for a class usually holds for every class that borrows its rules. 8 of them publish no component rules of their own and are marked below; for those, the link to the parent class is read from the categories table rather than stated in the rulebook.
Not permitted, not listed in the rules Our reading, not a rule we can quote at you. This class requires the craft to stay stock except where the rules allow otherwise, and this part is not on the list.
Not permitted, not listed in the rules 9 classes
Not listed in this class. Illegal under the class's own stock clause.
Not permitted, not listed in the rules 2 classes
No ballast article.
Governed by the parent class 8 classes
No component rules are published for this class and no single parent class is named, so this part cannot be answered for it. That is an absence in the rulebook, not a permission.
Legal, within limits 3 classes
Constant mass only, within the normally exposed areas of the hull, no fluids, requiring no modification or relocation of other parts. Weight control is performed with an empty fuel tank and all other liquids at race level. 501.04.05/.06
Legal, within limits 2 classes
Same. Ballast may be added prior to competition to meet the 300 kg minimum. · 502.04.02-07
Ballast weight kits: if the rule your class applies reads differently to you, or the rulebook has changed since this was read, ask. We answer with the section we read it from, or that we have not read it. Ask a rules question.
Every UIM class · where the rulebooks differ · signed checks on parts the shop sells.
Hull and handling · two and four stroke · legal outright in 5 of 24