The optimum length to width ratio of a streamer is a metric for optimizing the descent rate of a model rocket under a streamer. Descent rate is a function of the mass of the model rocket (including mass of recovery device) and the "drag force" created by the streamer.

Streamer optimization studies were conducted over the last several decades all suggest that there is an optimum streamer size. More width = more drag and more mass. More length = more drag and more mass. A little streamer does hardly better than blow nose recovery. A huge streamer might be too heavy and the model rocket's peak altitude is compromised. Somewhere in the middle is an optimum range.

The body tube diameter doesn't even enter to this function, so it is irrelevant.

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-Wolfram v. Kiparski
NAR 28643 - TRA 15520
MTMA Section #606 President