An alternative to the buddy seat is a trampoline.
It is important to realise that trampolines cannot be used when racing in Challenger events. The standard SI's include the statement "helm and buddy should remain seated in their normal positions within the main hull or on a buddy seat or similar except temporarily in an emergency". The reasoning behind this rule change is that a buddy on a trampoline can give a significant improvement in performance by changing their position on the trampoline (particularly by moving out to the windward sponson), whereas a buddy who is by necessity on a buddy seat, because of the needs of the sailor, can gain no such advantage.
There are no commercial suppliers of Challenger trampolies. They are made from the same material as catamaran trampolines. They are approximately 1.05m x 1.55m. Along the short edges are cringles at approximately 150mm to 200mm intervals. They are fitted by running a long length of line backwards and forwards between the cringles as shown in the photos. It is important that this line is pulled as tight as possible ortherwise the trampoline will sag and the buddy will get wet (which is not popular!). It may be necessary to tighten the line as the sailing season progresses.
Only one trampoline is needed per Challenger as it is difficult for the buddy to switch sides when the boat changes tack.
One advantage of a trampoline is that the trim is improved as the buddy is further forwards compared to the buddy seat. A disadvantage is that it is difficult for the buddy to reach the tiller for this reason it is recommended that a trampoline is only used with sailors who are almost ready to go solo or sailors who can reliably obey instructions including visually impaired sailors who just need a sighted guide.
Remember, trampolines cannot be used for racing in Challenger events.