This is how I say it:
“You have twice the experience I have”
to me it feels right, but searching examples on the net, I don’t quite find a similar example. I could rephrase. I think these are safe:
“You have twice more experience than I have” or “You have twice as much experience as I do”
but back to my original way of saying it, is there something missing before “I have”?
“You have twice the experience that I have”
It sounds better without the “that” to me.