Metal roof coating

I used Henry's SolarFlex on my metal roof at the recommendation of friends. My friends used Snow Elastometric on a Class C and the Henry's SolarFlex on their bus. The temperature difference with both products was amazing. But I think the Henry's is slightly better or it was just hotter in NM. Neither product is rated to withstand "ponding" so if your roof sags, then you need to fix that. I just don't understand why the RV manufacturers insist on building a completely flat roof when they could build a roof with a slight bow in it and still have everything on the roof fit fairly flat. I used the residential roof coating because I like to know that I can buy more roofing stuff most anywhere I am. Same reason I have mostly replaced everything in my vintage RV with residential components. I object to paying more for often lesser quality stuff simply because it says RV on it.