Supsoulrider said..
10 inches DJ
10" should be about right..
What happens when new people start paddling is they keep their upper body pretty still and upright (to help themselves balance) using just arms to paddle.. You need a slightly longer paddle to paddle with this technique..
Once you learn to lock out your arms and throw your upper body weight into each paddle stroke you automatically start bending at the waist to take a stroke.. Once you start using this technique you need a slightly shorter paddle (like you have) and once you start perfecting this technique you might need to shorten your paddle even more..
IMO you should not be bending over (or hunching your back) to get the blade fully dipped but hinging from the hips and sticking your butt out as you lean forward.. Doing this should protect your back from injury and give you more power..
Paddling more in glassy conditions helps you concentrate on technique without concentrating on balancing at the same time..
What board are you paddling?