i did a lot of research, cos i had the trophy air 6 before I had the twin club, but everywhre i read that they weren't compatible.
i'll be honest and say i can't remember if it had the regular modulo-clip fixings or whether they were slightly longer/bigger.
I guess it's possible that you could force it onto a trophy chassis.. the problem is that it would maybe make it unstable. the chassis for the twin club is a reasonable amount longer than the trophy chassis so that the end doesn't tip down, so i wouldn't b e happy using it like that personally just in case.
it was fine to push on even ground, but not easy to get up curbs. pushed round town like a dream! (and had lots of comments on it!)
any tandem pushchair is going to be heavy up front though simply because of how they're built
you ideally need the lighter child in the front seat, which means your newborn is far away from you! I had ds3 in a carrycot on the front, with ds2 in the seat facing me, but that meant I couldn't recline his seat because the carrycot was too long. when they were both in seats I had them facing each other, which was nice, but as I say, your smaller baby is furthest from you.
also, it comes with a raincover for each seat. which is fine in theory, except for when it rains the rain runs off the covers, between the 2 seats and down into the shopping basket and makes your shopping all wet.