I am a homeowner with a Lazer Z purchased 8/2001. Having frequent flat tires (mainly front) due to thorns from locust trees, etc. Have tried SLIME in tires, but doesn't seem to work very good. Tires now have many plugs each. Saw similar looking tires in Northern Tool catalog that were supposedly solid rubber. What does ExMark know about the use of solid front tires, or what recommendations do you have to help eliminate the problem (other than obviously removing the trees).