.tgz vs .tar.gz the double compression may cause issues. and folks not understanding (same thing just different way of showing it. as far as i know?
.tgz = tar first, then gzip
.tar = tar
.gz = gzip
.tar.gz = tar first then gzip
for 7-zip = adding to archive (via right click) and choosing tar then click ok, then repeat but choose gzip next then ok and then if need be rename file extension?