main cap walk

I recently tore down my 383 --> 489 stroker and found evidence of cap walk on every main cap. For that engine, I had the crankshaft gun drilled to lighten it up. Engine was probably just shy of 500 hp. The block was line honed before the build. It was a 440 source stroker kit, balanced by them. I used arp main studs (it was line honed with these in place) and stock main caps. On tear down, the main bearings all showed signs of wear, with a little copper showing on 2 of them. Rod bearings were all mint. This motor saw 6,000 rpm regularly over the course of about 12,000 miles, but I really didn't expect to see cap walk with this relatively mild build, especially with main studs and a fairly light rotating assembly. Going by ear, and looking at pistons and plugs, there was no sign of detonation ever.
The new build will probably be roughy 100 more hp. So the question is what to do to keep from blowing it up. Just run it and forget it? Girdle? Aluminum main caps? Blame it on the balance job on the crank and get it re-balanced? Was it the cheap 440 source fluid damper I used?
I'm leaning toward a 440 source girdle with my stock main caps as cheap insurance. And just like any other insurance, I'm not sure it will help lol! Aftermarket block isn't really in the budget, but from what I've read I shouldn't need one for 600 hp. Let me know what you think. Thanks!
-Jay