Been home-porting my heads for well over 20 years. Only way I have to test is "before and after" ET slip comparisons. 3-4 tenth drop is what I usually shoot for. Not sure I get every spot right, and I also port on the conservative side (not removing too much). Always just looked for modest gains.
see that's it without a flow bench you're basically sticking a certain size socket in the hole LOL and using a measuring device on the openings... I would think the only way to get the stuff extremely even is with a flow bench...
mindlessly grinding away for days is not my thing and even PBR doesn't do it for anybody else because it's not fun... maybe having a little fun with the speedmasters because it's new to him but the Lester will wear off fast I'm sure...