How much can you stretch a hat?

[JDCrockett]

Howdy folks!
I have a question and if its already been asked and answered feel free to redirect me. How much can we stretch a quality felt hat? I'm always seeing hats I'd love to have on Ebay that are smaller than my 7 3/8 or 7 1/4 long, can I expect to make a 7 1/8 work without removing the sweat band and liner and having it reblocked? Is it possible to stretch a sweatband that much or will it need replacing? Ahh this hat addiction!
Thanks in advance for you advice and comments!

 

[Aaron Hats]

I've stretched a hat two sizes, without distorting the hat or ruining the sweatband, though I prefer to only go one size. This was using a hot block, not a wood hat jack.