I want to make Knitty's Toasty Topper (http://knitty.com/issuewinter07/PATTtoasty.html
) for my son, but he's almost five, and has a big head, so I'm thinking I need to make it a little bigger. Do you think using bulkier yarn and bigger needles will be okay? I know enough about knitting to know you can do that with some stuff, but not enough to know whether it works in every case? What do you think?