[SteveCallas]

Maximum port velocity achievable without producing chuffing is not a concrete number for all port diameters - it varies by port diameter and the flare radius. The larger the diameter of the port and flare radius, the higher the speed you can get away with without experiencing chuffing. Collo's "Flare It" program (which I believe can be found on this forum) does the math for you, you just input your flare properties. His program will also tell you when compression starts setting in.

As for first resonance, based on experimenting done by various LLT owners, I'd recommend you keep it higher than 190hz when using an 80hz crossover. This roughly equates to a port no longer than 36". The shorter you can make it while still having enough port area to avoid chuffing and compression, the better, which gets back to using large enclosures.