[Mr V]

In my 3 years of being associated with FIRST I've never seen them do a weigh-in of spare parts at the Oregon or Seattle regionals.

It sounds like you are not going to be in compliance no matter how you cut it with your current plan. As noted the limit is on fabricated parts not COTS. So if you were bringing in an arm or claw for example as a fully assembled part the entire assembly would go to your 30lb limit. If it was carried in unassembled then the hardware, motors, cyls ect would be considered COTS items and not be limited while the parts that were machined, cut, and/or drilled to the final configuration that will go on the robot will be considered fabricated.

In your instance the parts that make up the cover are already cut/machined/drilled to their final configuration to go on the robot so the only thing you would save in weight would be the fasteners. Ditto for the bumpers.

So I suggest taking apart that cover, leave home the largest/heaviest parts and fabricate those on site in accordance with the rules.

If you have tool or person power limitations of getting it fabricated on-site look us up and we'll be glad to help in any way we can.