We were wondering if robots are allowed to extend above the basket on the top of the pyramid while climbing. We are planning to dump the discs into the basket. 
I have not found a rule against it.
Looking at the scoring levels, level 3 extends pretty high.
84" won’t get you to the rafters, so looks like the high altitude dumpers may be viable. Throwing discs up there requires dead-center accuracy or they’ll just skip off the chain(s).
Official Q&A 32 says:
Q. Is the section of the pyramid above the Zone 3 border as shown in Team update 1 considered a separate zone for climb legality purposes? For example, would touching the pyramid above the Zone 3 line while still in contact with the zone 2 bar be considered a violation of the Sequential zone rule or the 2 zone rule?
A. There is no upper bound to Level 3.