Does r4 mean that we can’t have any passive attachments hanging outside our robot perimeter? What about a scoop?
R4 governs the Starting Configuration–as in, when you place your robot on the field.
Once the match begins, R3 takes over and allows you to extend 15" past the frame perimeter (not the bumpers, the frame perimeter).
You can have those items, but they have to exit your frame perimeter after the match begins. This requires them to be at least somewhat active (in order to drop down after match start).
This rule (or a reasonable facsimile) has been in the FRC rules for quite a while, with a notable exception for Recycle Rush, which had no frame perimeter/bumper rules.
It’s really just a re-enforcement of the frame perimeter definition: every part of your robot except the bumpers must START inside a convex polygon that is no more than 120" in perimeter, and has no articulated parts. If a scoop reaches outside of the chassis at the start of the match, the scoop defines that part of the frame perimeter.
The wood and noodles of the bumpers must be outside of the frame perimeter and be backed by (securely touch) the frame perimeter at least every 8", and 8" to either side of a corner or curve in that convex shape.
If that scoop starts inside the frame perimeter and drops outside later (whether actively through a pneumatic cylinder or motor, or passively through inertia as you accelerate away from it), that’s OK. Just note that anything which is outside the frame perimeter at any time is at the mercy of other robots ramming you at full speed; better to be able to retract it when necessary.
Edit: a response to a PM:
That’s how I read R26:
Therefore, if a gap is more than 8 inches wide, it must not be greater than 1/4" deep. Unless you have 1/8" thick wheels with less than 1/16" spacing on either side of those wheels (!!!), there must be a bumper support sticking out between each pair of WC-style 6" wheel, and with 8" wheels, you have to reach above or below the maximum wheel radius to comply with the rules.