Sean,
You can use them initially, but you'll find they're pretty aggressive and you'll likely get some chipping... there are other more expert turners here on the acrylics, but my suggestion is if you use these gouges, just use them to knock the corners off then revert to a good sharp skew... I think the skew does a much neater job, leaves a smoother surface and less likely to cause a blowout. I do about 90% of my pen turnings with a skew, and only use a spindle gouge to do the initial rounding on antler... then back to the skew.