Not a problem, it was a little over 3gig having just checked. Just give it a try and see how you get on, if you don't like it then at least you've tried and who knows it might surprise you.
Recording at 1080p/60fps
Lagarith - 4m:20s was 22gig
Lagarith - 2m:01s was 10.9
Matrox - 4m:05s was 3.2g
Now the quality isn't as good granted but the quality is pretty damn good still.
Heads up though if you view your files in VLC this codec won't work with it, something to do with it not supporting this codec. It works and loads fine in WMP and others though and is picked up by Sony Vegas/Sony Movie Studio fine as well.
I record the video+ gameplay sound in shadowplay and use DXtory to record gameplay footage (1pixel x 1pixel), teamspeak, my mic and gameplay audio.
Keeps dxtory file size down to essentially an audio only and having two gameplay audio channels makes lining up audio a doddle in sony vegas, then I just remove the DX tory 1pixel vid and the additional gameplay audio.
Leaves me with decent gameplay footage from Shadowplay (has been run through handbrake to give a constant 60fps output) and 3 sync'd audio channels.
I gave up recording gameplay footage on DXTory to use due to desync issues, couldn't get it to work after about 48 hours messing so just moved back to shadowplay.