Im 5'11, and a pretty well built 210. I had no issues tucking on my stock '03. Like several people before have said, start out slow, find whats comfortable to you, and work your way up.
I hit 16X on a portion of highway up north of where I live. bean fields on either side, no turns or hills. just a nice place to make a fast run.
Thats also where I hit 170 in my SRT, and just over 200 in my VR4. My little proving grounds I suppose
On a side note, the safest place to do any of this is honestly on a track...
*^^ Hypocrate ^^*