Save value host.fact into host_parameter, is it possible?

In my Satellite environment we are going to be using the Discovery ISO fo new machines. We will have various custom facts that people will enter at the end, one of them being paritionSizeSwap. Swap could also be things like "root", "opt", "var", etc. and are all optional. I have found that these values will show up in @host.facts['paritionSizeSwap'] within a template, which is great. But, to allow the value to be changed later if the system is ever re-built, I would like to move @host.facts['paritionSizeSwap'] to host_param('paritionSizeSwap'). Does anyone know how I would do this within a template? Is this even possible or are host_param values read-only?

I have tried putting host_param('partitionSizeSwap')=%= @host.facts['partitionSizeSwap'] %> in the provisioning template used for our OS install. But it seems that doesn't work.

Thanks for any help you can provide.