Leaders in Transports

[KirkH]

I've always been a bit fuzzy as to what things leaders can do while they're being transported in a truck or halftrack.  From what I see (or don't see) in the rules it appears their abilities don't change whatsoever.  So if I have a leader with a combat modifier being transported by a SPW 251 that is adjacent to another SPW251, can he use his modifier to add together the DF numbers of the two SPW's to perform a combined attack?