Yeah. Remember when they used hollow exhaust valves in medium and heavy duty trucks filled with sodium to keep them cool? Did it for a LONG time. Probably from the 40s to the 90s I bet. They finally quit. You know why? You know what happens when pure sodium hit any moisture at all? It explodes. Violently. The valve stems were cracking and exposing the sodium to the moisture in the exhaust and bam. They finally stopped that stupid crap. I don't care who makes um, or who runs um. I wouldn't trust a hollow stem. While the performance versions are certainly not sodium filled, use your imagination and think about how thin a 3/8" valve has to be that's hollow. I just wouldn't do it. I'd look for other areas to save weight. Just my opinion.