I've got a 360 and a normal buggy board. It works when I've got the carrycot on rather than the pram seat. Once the pramseat is on, you have to take the hood off so they can lean forward in front of the handlebar.
Mostly I just let him sit on the footplate, the pram steers better than with the buggyboard on!
Also, I don't know how old your baby is. Once the baby can sit up, you can fit both children in the seat next to each other or one in front of the other. Probably wouldn't do it all the time, but for when the big one gets tired or you are in a hurry.