Thanks all for your comments
Howard - last night was first light for the 7D, I used up to ISO 3200 and it was excellent at this iso too. I will have no hesitation using ISO 1600 for widefield work with this camera.
Shane - I focused using live view at about 2am and kept this focus all night - if I attempted to refocus during the eclipse liveview would have been useless it was so dim.
Im extremely happy i stuck it out with setting up the gear - evan while I was standing there with the umbrella shielding the scope/battery thinking "totality is in 20 mins... cmon cloud give me a break!"
Grahame.