It has to be 5cm x 5cm x 2cm. Make it out of anything that doesn't bend (we 3D printed it with a high infill but you can just as easily cut it out of wood). The weight will be negligible in testing and should be part of the weight held. You do not necessarily have to have lateral force but that will depend on your design. Even with a bridge design from last year, the lateral force was not all that much. Gravity will act to "secure" the loading block to your bridge.That is the first thing that pops up to me. What should I use for loading block? What material and weight? Because there is a lateral force here, and it is not secured. How do I make that stable enough to hold the maximum weight? Hmm, it could be a pretty big factor here, or maybe not....Yes supervisors are great people and I thank them over and over again for taking the time to make this happens. So I am not at all suggesting that they are bad people here, I am merely suggesting that if they coach a team also, they have access to the actual apparatus and loading blocks while we don't. If the rule is designed so that those things are factors, then that could be a little bit unfair.
The problem is that it would be impossible to regulate what the block material is. Even if you say that it must be "wood" there are many different types of wood. Ultimately, as a coach, I would say worry about the things you CAN control and let everything else fall into place. Take Electric Vehicle as an example. If your gym floor is more like the floor of the competition, then that's awesome. But, we/you cannot control this so be ready for anything.