I would use a half insert for the front of the shoe. I have had similar issues when I buy shoes because they are the only size available or when shoes stretch out.
Another thing to try -- For some of my big shoes that I wear frequently, I find that the 1/2 insert flattens out over time. Instead of constantly replacing it, I have brought my shoes to the cobbler to have him add a permanent 1/2 sole in the front of the shoe. It is placed underneath the lining of the shoe so you never even know it's there.
I prefer the sole inserts over the adhesive heel grippers because I have found that the heel grippers leave a noticeable space between the heel and the shoe.