Formation flying is certainly a lot of fun...and about the most difficult thing you can do in two aeroplanes...it takes a hell of a lot more concentration than you would think before you've had a go at it.
Myself and two friends did a formation rating about 18 years ago in three C152s...the school where we were learning ran the course with three very experienced instructors. We initially took off seperately and formed up later but after a few hours were never seperated by more than about 6 feet from brakes release to touchdown..wings overlapping all the time...when you get used to it closer is easier than looser...up to a point
Relatively underpowered light aircraft make it a lot harder.
In the intervening years I've done perhaps 20 hours in formation, including some at night, which hardly makes me an authority.
But to just 'have a go' is fraught with danger as you do not necesarily use the controls in a 'normal manner' while keeping close formation...use of aileron can lead to some pretty scary 'illusions' in terms of position relative to the lead aircraft for instance.
Get some training before you hurt yourselves!
Chuck.