I've chased a bunch of chronic leaky nose seals in my time, so I guess this is a good place to pass along some hard-earned knowledge. For chronic leaky seal situations, consider these two mods.
If your seal has spun, and you're confident it was installed clean and bonded well, you might consider using Proseal. Everyone I mention this to says, "OMG! You'll never get it out." Not true. It bonds very well, yet is still removable.
If your seal stays bonded, but still leaks, I suggest shortening the spring by ~3/8 - 1/2 inch. To do this, just cut off the appropriate amount from the loop end of the spring. Bend over two new loops 90-degrees to the spring and attach as normally intended. Will provide more sealing force.
I've done this on quite a few seals over the last 10-15 years and never once spontaneously combusted or perished mysteriously, yet.
Last, someone mentioned the "retainer plates" on the nose. The newer engines casings are generally cast to accommodate these. Some are drilled and tapped (1/4"), some not. And some of the older casings have drilled and tapped smaller holes (3/16"). So, it varies. But I do like having these plates installed.