[buchanan]

Maybe I'm just "borrowing trouble", but this looks to me like a loophole through which a team could bring two alternative mechanisms to the competition, present only one for initial inspection, then swap in the other if they decided the first wasn't as effective as they'd thought, effectively giving two shots at picking the best design.

I guess at some point you have to just trust people to adhere to the spirit of the rules, but it seems to me it's better to get as much into the letter as reasonably possible to forestall temptation. The "add but not subtract" approach would do this, albeit at the cost of loss of modification flexibility being the price of squeaking in under the weight limit initially. This does not seem like such a bad thing.