i have teeny-tiny hands – i cant even wrap my hand around a 45mm. I pole on a 50mm and my hand only can wrap around about half the pole, however despite my small hands i am super comfortable on this! i would give your 45mm more practice for few reasons. the first being although you may be able to get a tighter grip on a 40, its going to really dig in whenever you try to do anything. also you might find that in future if you for whatever reason you need to use a 50mm you will ave no clue how to use your hands. i think 45 is a great size because it’s common in comps and its sack in the middle size 🙂 i would just keep practicing and honestly not bother about the 40mm!