I only see round holes in chasis. round holes at a small to moderate size do nothing to weaken a steel beam. square holes on the other hand would present changes in a beam.
PS looked at your gallery nice red trucks! your 99 xlt looks far from beat up. I do however wish I bought a 250 series or better pickup. Since I have this one my mission is to use it up and kill it before getting a new one. my truck is a work truck but my trailers take the abuse of tools and cargo now.
I want to get 200,000 miles on it before replacing....I have 48,000 and still is in good shape see my gallery
http://www.f150online.com/galleries/....cfm?gnum=2890