Fiber Cement Siding – Outside Corners?

I am in a bind regarding the above. My project is a major remodel on a 1940s Cape Cod in North Central Wisconsin. Cedar shakes are coming off to be replaced by fiber cement [7 1/4 maxi planks]. Sheathing is ship-lap pine in good shape, with old felt being replaced by housewrap.
Homeowner requesting that outside corners have metal caps to replicate look of cedar shakes.
Architect says ‘follow manufacturer’s installation guidelines’.
On-line manufacturer’s installation guidelines indicates corner boards for inside & outside corners. No references to any other approach. I emailed Maxi-Tile customer service & am awaiting reply; given their on-line manual, I suspect I’ll hear something along the lines of ‘go ahead, but may void warranty’.
I’ve scoured other F/C installation manuals. CertainTeed & James Hardie show corner boards only. PlyCem does give option of metal corners on outside. I found one on-line supplier [prosidingaccessories.com] who sells metal caps with epoxy finish on inside.
Two questions for you:
1. Anyone with any experience with such an installation? I know F/C has little to no vertical flexibility, so labor costs here may require a work order change.
2. The homeowners are reasonable folks, & I’d like to accomodate their request. If installation voids warranty, do I get some agreement in writing re being held blameless should siding fail?
Replies
I think these corners are what you're looking for. http://www.prosidingaccessories.com/
Fibercement is more work to install than most other siding, but using metal corners may make the installation job easier than using corner boards. I cannot imagine the metal corners causing any type of failure, but I would prime the ends of the siding as you go to prevent water intrusion as extra insurance.
IMO, if the mfgrs try to claim that "tin corners" void the warranty, they'd dodge responsibility some other way without that excuse. "Tin corners" are virtually foolproof, and more reliable than just about any other technique.