Hi Stamcel,
I am in the same situation except my LO has never really napped - in his whole life! (8w) Like your baby, my LO also sleeps very well at night - 6:30 til 2ish (with a DF) then again til 5ish.
Our lives were living hell as it took about 30-40m of screaming before he would settle when nap time came, he would sleep for 20-40 if we were lucky and then another 30-40m of screaming when i tried to resettle him.
It was breaking my spirit.
This week I tried a new tack - we started the wind down about 30m after he woke from his nap (any nap, even the first waking of the morning). That way he was only awake for about 50-60m before he went to sleep. He is a hyper alert little fella so any more awake time than this was simply killing him. (I didn't realise this until a fellow poster pointed it out to me.)
So far, day 3, it seems to be working 9 times out of 10. It's still a major drama getting him back to sleep after he wakes from his 45/50m naps but at least getting him to sleep in the first place is easier.
I hope my experience gives you at least one new thing to try; god help me, I would try anything if it meant my LO would just bloody well go to sleep!!
Bec