Do not file the edges of the brass throttle or choke plate. If you examine them closely they have an angled edge that fits the carb bore,they cannot be reversed either,when installing one you have to look closely at it to get it in right.
Since the 80's I have been boring out the stock carbs-HS,WJ,and HT. Depending on the model I've gotten 33% or more extra flow.
These work great,a stock saw carb is far too small so any improvement helps a lot.
Thinning the backside of the throttle shaft is ok and picks up some flow,and sometimes you can file the screw a little flatter too. If you remove the shafts you can polish the bore and remove any casting ridges or defects.
Next spring I will have an even larger version of the WJ,with larger bores and plates.