it would be ok to probe larger garters, but it's not necessary as larger garters are easy to sex visually. I pop all my babies and have been 99% accurate! It's very easy and rather safe to pop them once you get the feel of it just a gentle roll of the thumb and if it's a male it will pop, lol! They'll all pop a little musk on you lol! You gotta remember snakes are tough critters made to handle rough terrain and as long as your gentle you shouldn't hurt them as it takes very little pressure. It's really more about technique on how you roll your finger. Now I never pop snakes over a couple months old as they start to gain more control and it gets harder on them. I will say this it is almost impossible to visually sex babies as some that look female with a nice taper can still be male and will start to show later on. Hope this helps!