Re: Insulation/Stud Spacing
Depends on the methods for the area , who built the home , etc. ... 16 inch center spacing was widely used back then but could also be 2 foot spacing.
Pick a referance like a known original location of an electrical outlet ....with your tape on the left side of the electrical box ( normally the boxes are secured to the right side of a stud ) measure out to the right 15 1/4 inches and see if there is a stud .... if so they're 16 inch spaced..... if not measure out 23 1/4 for 2 foot spacing.
As you found out ... it's easier to find the cavities than studs.
I take it you will be blowing in the insulation yourself ... there may be cross blocking midway up the wall in which case just do 2 holes .... one high and one low.
"" an ounce of perception -- a pound of obscure "