Hi again,
I think if you are really struggling with the catnap, I would try extending the other two naps, and then see what happens, maybe he will be OK without the catnap, or he will be less overtired and go down more easily for it. I would concentrate on this, rather than holding him for his catnap. I understand the theory behind it, but I'd be concerned that he's realise how nice it was, and start wanting it for other sleeps (dangerous as it's so close to bedtime :wink: ). BTW - my ds still has a catnap at nearly 9 months, he couldn't make it to bedtime without it, so don't feel pressure to make your lo stay up when he doesn't seem to be able to.
You mention that he gets a catnap maybe 3x a week when you are out - how is he then? Less overtired at bedtime? Less cranky? If so, then he still needs it.
I think the best thing you can do is work for 2 solid naps a day of 1.5-2 hours, and the idea of a 'quiet-time' is a great one. What are you trying to extend naps? Do you need help with this?