Cloudflare with SSL

Hi guys,

i am wondering if there is a reliable way to use cloudflare with a custom SSL certificate but on a free plan.
I read that they say old systems like windows xp will have trouble accessing SSL protected pages. What is your experience with that?
My client's site needs SSL but we are not up for a $200/month plan at Cloudflare.
What do you think?

Warm regards,