[Brian Duff]

I would go with aluminum blocks . Unless you plan to polish those stainless blocks on occasion, they will look worse 20yrs down the line than aluminum ones. I think that the anodizing on alum blocks looks more like orignal conditon after that long, than stainless blocks which are often brown and look much more like they need to be inspected and cleaned. Plus, aluminum blocks are often lighter.
Some manufactures have blocks which avoid stainless all together by using lacings and grommets of hightec line to secure them.
I really like spectra. I recently had a big 'cat' customer go so far as to get pre-streached spectra shrouds and use dead-eyes/lanyards intead of stainless/bronze turn buckles, to battle weight and fatigue problems.