Is the viper .177 or the .22 , I have a viper in .177 and replaced only the scope,I reused the mount which I believe to be a accushot medium,I put on a Tasco 6-24x42, And had to drill the riser so I could shift it as far back as I could because I chose a very long scope,but I think you will be just fine with a 3-9, And welcome to the GTA and remember there are no stupid questions here