When you say you rubber banded a bit of card i'm assuming that was to act as a white card refector? ie, a small flat bit of card on top of the flash head pointing straight forward so when the head is rotated up the light will bounce of it towards the subject correct? or did you bend the foam around to make a soften style flash head?
In either case you'll quite often get harsh shadows, the perpose of the white card refectors is ususally to add a little direct flash to the subject to add a highlight to the eyes, lovely for the news papers but i find not so good for wedding shots, the soften style diffusers can be quite good if the ceilings are very high or the subject is allong way from a surface to bounce off, but for me if your going to bounce the flash, blounce it from where the natural light is coming from, your pictures will look natural but with better lighting, i also like to add a bit extra to the flash to really make the colours pop.
At a recent weeding i was talking to one of the bridesmaids and she was asking a few questions about why this and that, one question was why was my flash pointing all over the place!
I took the first shot to show her what the pictures would look like if i just snapped away... then i took the second shot to show her what my pictures will look like because my flash is being used properly...
1. Direct nasty flash!
2. Bounced flash with no flash head reflectors or soften diffuser.
Not a wedding sample but if you look in the lttle girls eye you will see the big light pool created by the bounced flash oh yeah and me too lol, so it no wonder all the shadows are soft.
Canon 5D MarkII, 40D, 350D, EOS100, G10. Canon 24-105 F4 L, 85mm, 400mm F5.6, 50mm F1.8, 18-55mm, Sigma 10-20, 100-300mm, Canon 28-105 F3.5-F4.5, Kenko x1.4, Tubes and a bunch of Elinchrom Lights, flashes, reflectors and triggers.