Discussion of when rebuilding the catalyst, it's better to use a spring

I wanted to discussion of when rebuilding the catalyst, it's better to use a spring so I can have a better understanding of the pros and cons.

For instance, am I to understand that:

Generally the spring holds more lightly packed catalyst material therefore creating more heat than if I just rebuild with a flat cut piece of or even several layers of new platinum catalyst?

Is the spring design better at catching all the rising fumes so there is less unprocessed fumes/waste and so less raw fuel odors?

Thanks for the discussion!

Jim,
I'm not a big lover of the spring method of holding the catalyst. I find that loose pack is more desirable and seems to work best. With loose pack the fuel vapor must go thru the cat because is cannot go around it. Be sure to use the keepers, I'd necessary, to keep the Cat off the fuel soaked packing.