Gray tank neck crack (is patching possible? Plasti-Mend?))

My gray water tank had a huge hole in it right by the drain spout. I bought a new tank and was going to have it installed but in the mean time I bought some Plasti Mend. I fixed the gaping hole with the Plasti Mend that was 4 years ago. My new gray water tank is sitting in my shop up in the rafters. Waiting for the Plasti mend tank to go out.. I have traveled over 20 thousand miles with that mended tank and it works perfectly to this day. I don't think it will be going out any time soon. My gray water tank is Black ABS