daytime soccer

Hi guys,

At a semi pro level of soccer, I have field access to game, to shoot for a local pro team, Im using a 7D,manual,2 lenses,70-200 2.8, and a bigma(50-500 sigma).

in bright sunlight the bigma is fine, getting 1/2000 at 400iso,sharp pics ok, soon as cloud covers,its terrible noise wise,noise ninja helps, but i hate "fixing" images, just like to get it right at start,

the 2.8 is obviously heaps better, but not long enough really,

is it acceptable to use a flash at semi pro level during daylight? i dont want to dazzle players? but notice other appear to use a flash?i thought it may be bad etiquette?

i need to improve my keepers, and cant afford a 400 is 2.8!

any suggestions?? tried iso up to 3200, just too noisy.

want to stick at 400 iso if possible, slow shutter down a bit ,maybe 1/800??

Nick.