"I think there are a few things that influence the "test" described above - I found out when making a stock for my wife, that the grip shape has a lot to do with where the trigger finger reaches or lays"
This is very true.
Most commercial rifle stocks with a "pistol grip" build them to appx fit 90% of adult shooters.
The new trend in stocks has gone to 90 degree pistol grips, which many folks find uncomfortable to hold.
When I was taught to shoot, we were taught to pull the rifle back into the shoulder with the extended hand on the fore stock.
Using the "pistol grip" to control shoulder contact is fine, from a rested fore arm, but not great for offhand shooting.
This is just my personal preference of course.
Yes, some people insist on using the hand that controls the trigger to pull the stock back to the shoulder as well and they shoot very well.
It's all about personal preference.
Good on Potashminer for going to the effort to make that rifles more comfortable for his wife/grandson.
Stock lengths are a personal preference and what suits one individual will be uncomfortable for another, even if they have close to identical physiques.
I have a friend with an extremely long neck and short arms.
By my measurements, his trigger length should be 13 inches.
Stocks this short cause him all sorts of discomfort during recoil.
His stock has a 14 1/4 inch pull length and he's always "reaching" for the trigger.
He shoots well enough, simply because he isn't afraid of the recoil and possible "scope cut" that is a real issue for him and his extra long neck.
Other folks like to hold their head right at the butt of the stock, often because they are right handed but left eye dominant and this allows them to use their left eye to shoot.
The list goes on.
Each to their own preference is fine. If it works and is comfortable, go for it