Sounds like a pretty clever solution. If you have the technology, then welding can work for you. I wouldn't think you would necessarily need blocking under the post, but it could come in handy for getting the height exactly right.

I used a plasma cutter to punch holes in my stainless post straps, once I discovered that you can't drill holes thru 3/16 stainless very easily! I have a few scorch marks on my post bottoms. (OK, I admit, some were on fire for a brief moment.) In short, be careful welding next to your timbers. They can catch on fire, but they'll probably self-extinguish.

Do you play bluegrass or just like to listen to it?

-Thomas (in the bluegrass state)