exhaust port

Hey guys, I'm wanting to put a side exhaust port on my 372 muffler instead of the top port... tired of it burning my hand when I've got the bar buried bucking big logs. What size should the exhaust port be? Not really looking to get max power, but a performance boost would not be unwelcome...

Ok here it Goes. I have a Stihl 045 and 036 that both experienced piston and cylinder scoring on the exhaust port side. I used 93 octane (4gal) and (2) stihl 2 cycle mixes (orange ones). FS trimmer is fine 55 series blowers are fine and the ms210 as well. All have used the same fuel. I was...