To be honest without spending gazillions s_m you re not going to get the best shots. Better to have a cheaper long lesna nd just wait untill the play occours on your side of the pitch so you can shoot at a wider (therefore faster aperture) setting. I got this from the uppermost teir at Wembly with the cheapest Tamron 55-200 lens, using the Sony alpha zoom thingum (for a change)
i ve not been lucky enought to get my mates to "pose" for me yest so I'm not so good for the MTBing, although a remote flashgun woudl help hugely, other wise you ll just have to use that "dappled light" photo effect that MBR is so fond of!