Mark, no I didn't have any issues with the airframe holes. The Grove mounting kit fits the original (SS7) airframe holes perfectly. In fact their kit continues to use AN-3 bolts, and I haven't heard of any problems with this, probably because their setup uses the shear strength of two bolts rather than one in a side load impact. Since I had earlier changed to AN-4 bolts my airframe holes were enlarged to fit the bigger bolt. When I got the Grove kit it was a simple matter to drill out the holes in the new Grove bracket to fit AN-4. So my tailwheel spring setup now is Really strong.

If you stay with the original spring and just go with AN-4 bolts, I would still put a bushing around the bolts and just file/grind a flat spot on one side of the bushing to fit up snug against the side of the spring. In fact a large sturdy bushing, round or square, filed on one side to fit, is in my opinion a real good way to go because it give more stability and support for the clamping plate on the bottom. I believe Floog did this with good results.