Replying to Tips for editing/rendering avchd-go pro

Hey guys just wondering whether anyone had any tips for editing 720p 60fps footage with sony vegas pro.

I have a 1.66 core duo w 4gb ram windows 7 64.

My machine gets pretty choked when trying to edit. I tried converting to HDV (m2ts) files but there was a big loss in the HD quality.

Anyone got any decent settings for rendering 720p 60fps avchd(mp4) where its editable but still POPS.
ie; should I convert it to mp4 30fps w a lower bit rate eg; 10mbps with a 4mbps average or is this too low. I tried uncompressed avi but files came out huge ie 100 times larger than original?

any help would be great.

ps; had a sick day on the whistler glacier today, day one. before camp of champs starts next week......