I saw a program on TV of some SOGs in the A Shau(sp) Valley with M-16 clips that looked much larger than the standard issue.

Some looked like 20 round clips and one looke like the current 30 round clip.

Where large capacity clips used on the M-16s back then?

Yes, and they are magazines, not clips.

When the M16/M16A1 was introduced, 20 rd. mags were standard issue. 30 rd. mags came out in '68.

Was not, and is still not, uncommon to tape two together. At a distance, the assembly will look much larger.

tapeing mags togeather is just as bad as adding all the outer space junk to an m-16. the rifle came as one of the fasted rifles on target around, why ruin its strong point. also if the mags are taped for oppsent ends you may shovel a bunch od dirt into the rifle.