The bumper itself needs to be at least 4.5" tall, as you’d find by looking at R402.
If you’re looking for the lowest the bumper can be, physics says you can’t go below the carpet.
If you want to know the lowest height of the top of the bumper, that’s at the top of the Bumper Zone at 5.75" from the floor per R405.
You must cover the zone from 2.5" to 5.75". After that, whatever you want
Would other teams be upset if one team used two deep cages to climb? It would get the ranking point if another team parks, but I’m concerned that it takes away a third climb during playoffs.
As your alliance partner, I’d be upset because you’d have consumed two CAGES and only gotten 2 points (for PARK).
6.5.2 says:
To qualify for CAGE points, a ROBOT must be contacting a CAGE (with the exception of the ANCHOR), not contacting the carpet, and may additionally contact only the following elements:
A. SCORING ELEMENTS,
B. another ROBOT qualified for CAGE points,
C. a partner ROBOT contacted by an opponent in violation of G428, and
D. an opponent ROBOT.
That is contacting a CAGE (singular) and only those following elements, none of which are “another CAGE”.
So, you’d then not meet the criteria for CAGE points and therefore this rule would apply:
To qualify for PARK points, a ROBOT’S BUMPERS must be partially or completely contained in their BARGE ZONE at the end of the MATCH and does not meet the criteria for CAGE points.
Where is the rule that says that the person at your processor is the opponent?
It’s in the field diagrams, as well as the Q&A I linked in another place you asked the same question.
Section 5.5 says it:
Once an ALGAE passes through the PROCESSOR, it rolls past a scoring sensor array and into the opponent’s PROCESSOR AREA.
Can more than one robot hang from a single anchor? (Citrus Circuits
had a robot that could hang two allies)
Can you design a giant claw like team 25 did in 2000, and steal algae from the opposing alliance? I think probably not, since reefs and barges are marked zones.
I believe stealing algae off an opposing alliances reef is a tech foul if any interaction happens.
Anchor, no robots can hang from. Semantics aside if you mean the cage the rule states that robot are considered climbed if they are hanging from the cage not touching the ground or touching an alliance member who is considered climbed which leaves me to reason that this is perfectly acceptable like the climbs in buddy climbs 2018.
(known as MAJOR FOULs now ) 
see G427, which @Ubiquity hinted at
note G410 (no descoring) only applies to coral
Only if they’re in the zone and hit you. And you’re clearing spots for them to score in, so there’s not as much incentive to hit you.
@Ubiquity hanging from the Anchor gets you a Major Foul and no RP.
How tall is the top of the rung holding the net on the bar? In the game manual it says the top of the barge is 8’5" from the floor which leads me to believe the manual implies the top of the sheet of polycarb between the two alliance nets, in the Solidworks playing field assembly the top of the rung is 7’4-1/8" from the floor
The team element upright is 89" (7’5") tall with the rungs pipes that hold the net less than in inch below that.
I think that the part of the barge that is 8’5" is the dividers that stick up above the net and pipes
Contacting two cages is still contacting a cage. If they wanted to exclude the use of two, they would word it to exclude the use of two cages to climb.
I agree with @sokoloff, while not said explicitly, contacting “a CAGE” is singular. Contacting multiple CAGEs would be forfeit all points gained by the hang.
151 submitted Q&A 19 directly asking this question. It’s not answered yet, but it’s clear and specific enough that I suspect GDC will end up answering it.
I have two questions that are vaguely connected…
Is there anything stopping a human player from throwing in algae after the match has ended? There is that 3 second window before the scores are finalized.
Even if the answer to #1 is that there is no restriction, is there going to be a strategy where teams that choose not to climb instead make a last second score in the processor? Algae that has been scored in the last second of the match will likely be processed in that 3 second window but not give the opponent human player enough time to score it into the net. Doing this would get you the same amount of points as a shallow cage (6 points). I could see a strategy like this putting a lot of pressure on the volunteer scorers to have to precisely count the end of that 3 second window should a human player be trying to throw an algae during it.
I had the same thought. I can’t find any rule against it, but there is precedent for FIRST nerfing “after dark” strategies
I predict this will happen sometimes, but probably more opportunistically then as a regular strategy. If they are allowed the extra three seconds, then human players can probably keep up, but it puts time pressure on them.
One reason that FIRST are likely to nerf it.
GDC could do one of two things to aid this:
