Kartra Split Testing Custom Domain?

I'm trying to split test two landing pages with Kartra, however once I create the split test, I am given a link that directs users 50% of the time to Lander 1 and 50% of the time to lander 2. The domain given to me is xxxxx.kartra.xxxx
I have registered a custom domain in Kartra, it works for all regular pages of the website.
Was wondering if I could use my custom domain to split test, instead of the auto generated Kartra one.

Thanks