RE: Stomach vacuums - any good?
Andy,i havn't done regular bench press in years mate,i never found it to be a very good chest builder.
Couple of things you can try,keep your arse and shoulders in contact with the bench at all times feet planted on the floor,pull your shoulder blades in together and down towards your hips,this will cause a slight arch but your shoulders and arse are still on the bench.That should cause your pecs to do more of the work than the front delts.
Arm spacing,when your upper arms are at the point were they are parallel to the floor your forearms should be pointing straight up to the ceiling,wrists and elbows in line.
If that doesn't make sense let me no and i will try and explain better.