it depends what you're talking about by "Vietnamese Centipede" ... I have seen probably half a dozen species/morphs called "Vietnamese" just in the short time I've been in the hobby. If the 'pede can be definitely identified as "Scolopendra subspinipes de haani", then yes, they get huge... just ask Bill Stanton (invertepet on these boards) ... he's got one that's on its way to 12". But a lot of times, S. subspinipes or S. subpinipes ssp. are simply called "Vietnamese" or "Malaysian" (depending on where they're collected), without much effort going into a firm ID. If you go with a knowledgeable dealer, they will be able to give you a positive ID.
As far as "regular" S. subspinipes (what "Vietnamese" and "Malaysian" usually are) goes... I would say that it's probably more accurate to say "may reach 10" ". The only one I would say for sure would hit 10" and keep right on going is S.s. de haani.
Other pedes that are available in the hobby that reach 10"+:
Scolopendra heros (castineiceps, heros, or arizonesis)
Scolopendra sp. "Hatian Brown"
Scolopendra sp. "Puerto Rican Giant"
Scolopendra gigantea - coming soon, Peru just recently re-opened for exports... they get 12"+