James, I can think of one install I performed in 2017 that was a metal roof over metal purlins and we opted to through-bolt the entire array using one installer on a ladder inside and another on the roof. We employed butyl mastic and large fender washers to attach a strut frame to the roof, and then we installed traditional L-feet and rails atop the strut. I have zero experience working with tile so I don't know what your best methodology is there but I can attest that the through-bolting has held up well at that site the past five years.
Sincerely, Sam Haraldson [image: OnSite Energy] <https://www.google.com/url?q=https://onsiteenergyinc.com/&source=gmail-html&ust=1677085494759000&usg=AOvVaw2NN36GoM1sjnS4RdC8Svt-> SAM HARALDSON Field Operations Director (406) 551-6135 1515 N. Rouse Ave Bozeman, MT 59715 Locally owned and operated since 2012 [image: B Corporation] <https://www.google.com/url?q=https://onsiteenergyinc.com/bcorp&source=gmail-html&ust=1677085494759000&usg=AOvVaw0EluC1lXtz2KlRFag-htKe>
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