After lots of tries, CD Accordion and CD magic tabs did it perfectly.
And when I asked for support to customize some features, they was quick and extremely effective, and it was 3 days before Christmas!!
Guys, you're fantastic.
This is definetely the best up to date. Works in multi-instance mode (you can have more than an accordion in the same article, each one running different layout and behaving), perfectly cross-browsing, fully documented and custonisable thrugh easy css/html.
I had an issue at the beginning: it didn't run in IE8. Asked for support at NinjaForge, they had quickly solved the problem, which was totally on my side (my custom template index file had invalid code I didn't even know!). They went much further than I expected in supporting me.
I already downloaded other 6 extension by NinjaForge and this is ALL for $10!!
Well, I would pay much more for what I got!
Great job guys. And you there... go for this accordion, you won't regret it.