Advantages of a second speedlite ?

I'm currently running a single 580exII speedlite either by itself or on a lastolite softbox and love the portability of this setup. Obviously when the sun isn't available or indoors I'm finding part of my subject isn't lit properly.

I'm using a Pocketwizard flex / mini setup to fire this, what about using a second speedlite mounted to the camera and angled to the opposite side of my remote speedlite ?

Mostly I'm concerned with what negative effects a shoe mounted flash would cause.

Thanks in advance !

If you're talking about using Canon's optical triggering system with ETTL, then you need to have a look at Syl Arena's book - Speedliter's Handbook. If done properly, minimal if any down side - especially when teamed with a long ETTL cord.

GeeMack wrote in post #13499746
If you're talking about using Canon's optical triggering system with ETTL, then you need to have a look at Syl Arena's book - Speedliter's Handbook. If done properly, minimal if any down side - especially when teamed with a long ETTL cord.

No I'm running a Pocketwizard setup Mini / Flex, I can mount a speedlite on the mini which is on my cameras hotshoe.