Parallels or VirtualBox to run Clampfit on a MacBook Pro running Yosemite 10.10.3?
I suppose the VMWare is also an option.

However, as you know with Parallels, you can restrict the resources that are available to Window, such as the number of CPUs available between Mac and Win, the memory, and the video card memory.

Whereas a typical configuration might be to share these resources equally between Mac and Win, in your case it makes sense to reduce the resources for Win (and consequently for Clampfit), and you can fine-tune this to your liking.

I'm not certain about how much you can limit the amount of hard drive space available for Windows. I always went with the suggested 64 GB, and I don't recall if you could reduce this.