Late to the party, but I am more of a KISS principle guy anyway.
Controlled Break-Away deployment. Plan on a rocket motor and design that easily meets and exceeds deployment altitude (and time if required.). Rockets don’t decelerate instantaneously, but depending on deployment Configuration, they can slow down pretty darn fast. If your first deployment is to break the rocket into separate components (connected by elastic tethers) and each with a streamer or other high drag attachment (chutes are likely to shred or break shock cords or attachments unless you have very long and stretchy shock cords.). I may be wrong, but I am guessing that breaking the rocket into 4 or more parts, each with a streamer, it is not going to gain much altitude (maybe 30 feet) after initial deployment. I don’t know the rest of the requirements for descent time (and I don’t know how well an egg payload would survive such a rapid deceleration.). Also don’t know how consistent it would be (maybe sometimes 20 feet, sometimes 50.)
the other approach is the “if you ain’t cheating you ain’t trying” approach. Again maybe the rule makers anticipated this. If the goal is to get a payload to a certain altitude, and the Score is calculated based in the ON BOARD altimeter, eject (but maintain attachment) the part of the rocket WITH the altimeter with a long (maybe daisy chained) shock cord just shy of target altitube, maybe with a draggy fin unit and a streamer. NOT sure if rules say this segment must contain the payload. Rest of the rocket, possibly with much of the mass, is now unstable (may still carry the motor casing), is tumbling and either the ejected segment or the traveling unstable unit holds the shock cord, trailing out, bulk of rocket continues up but is slowing down, finally deploys the chute. You may need 100 feet of shock cord.
point is, if you can separate the altimeter and if required the payload from the bulk of the rocket (think
@Daddyisabar tractor motors with payload and altimeter in the BACK) you can minimize the mass and maximize acceptable drag on the CRITICAL components of the rocket (I,e, the score-able segment) thus minimize (and possibly make more consistent) the altitude gain of the segment, with the long shock cord allowing the main mass of the rocket to make a more leisurely and less consistent (but who cares?) standard deployment. If your first component contains the fin unit (more mass but also much more inherent drag assuming unstable), then your remnant component will also immediately go unstable at separation and start slowing down by itself, prior to chute deploy,ent, so it won’t go far, and shock cord attachment will pull chute from upper segment prior to running out of shock cord, which will help.
point is, the ALTIMETER section upon which you are scored deploys just below target altitude, has low mass, high drag, and shouldn‘t go very far, so if your ALTIMETER is good and your ejection wiring system ignites initial deployment quickly, that section should hit (and stop near) target altitude fairly consistently. The REST of the rocket may travel another 100 feet, depending on length of shock cord, but assuming nobody is measuring from the ground, TECHNICALLY your MEASURED altitude is that of the initially deployed segment.
an additional option would be streamers attached every 10 or 20 feet on the long shock cord, so the cord itself also slows the non-scored rocket segment, may get away with shorter shock cord although need more space for multiple streamers.
