portage - the disadvantages?

[hoverfrog]

I've been reading avidly all the posts about portage, and apart from paying approx 10% of your hard earned earnings to them what are the disadvantages?

I'm looking at working a minimum of 4 days a month as a contractor (IT) for a Canadian company - would the client being out of the EU make a difference?

What happens if I take up other paid employment at the same time? (yes, I know, I should be so lucky in rural Limousin!!)

Is there a maximum you can earn where it's not feasible?

I can see the advantages, but there must be another side