I think the problem is.
1: (we dun know the shutter speed you have on your cam when you used the initial settings.)
Anything above shutter speed 1/250 will usually require high speed sync.
2: are you shooting to compensate for shillouette?
3: are you shooting to just make sure your subjects are lighted?
4: depending on how you position your subjects, is f4.5 sufficient depth?
5: if your flash is set at 1/1, is it because you are in M mode?
6: could you use a lightmeter to meter the amount of light needed?
alot of questions i guess. So maybe you could give us an example of your set up or show us the photo so we can better help you>?