What Flange?

Today I was trying to figure out the flange size that I should make up for my pump. Its a little confusing at first. You have to get to know your ASAs from your ANSIs( which are the same!) from your ISO-Ks and your ISO-Fs!
Now a 4" ASA/ANSI flange is 9" dia with a 5 and a bit inch hole. Maybe a 3" would be better...
Well to make a mornings research short. I'm going with an ISO fitting.
ISO-F 100 specifically. So here is a rusty piece of 6mm thick mild steel I had knocking around. I got the dimensions from the Net and marked it out.

After a bit of cutting and loads of grinding I got the disk below. I've just drilled the pilot holes for the bolts. I'm going to see if I can find a hole saw a bit less than 100mm to cut the disk from the center.
Looking good so far!