IMRs said:
The vendor sold me 2 ICR 18350's and said that these were recommended by the manufacturer. These batteries are grey in color and 'Special Lithium Battery' is printed on them (Made by D.K.L. Battery). He also said you can stack these batteries...My question is... are the icr's safe to use in the VAMO?

OK, this is going to get even more confusing. Some mods
are designed to accept stacked batteries. I won't even attempt to list which ones are as I don't know. I found this thread
ICR batteries... all protected? when I googled "DKL battery". There was some discussion and confusion on that thread whether these batteries, which sound like the ones you have, are protected or unprotected. There was also discussion about these batteries coming with the Vamo and being able to stack them.
Ordinarily, and you heard right, stacking batteries is considered to be risky and not recommended. Some mods are designed to allow stacking, their processors are designed to operate in that mode. I don't own a Vamo and don't know if its safe or suggested to do so. I'm not familiar with the DKL batteries either. Unless someone else more qualified than me wants to step in and give sound advice, I'd use a single battery over stacking two shorter batteries. That's just me, as I tend to lean to the safer side of things rather than the grey unknown side. At this point I haven't been convinced if these are protected or unprotected ICR or high drain batteries.
IMRs are used in regulated mods that use buck boost circuits to achieve variable voltage-wattage. This class will have less capacity in mAh rating compared to protected batteries, but are superior when maximum load current is required (high drain), such as in regulated mods, or mechanical mods using a Kick, or using an RBA.
The option (and possible risk) is yours whether to use these batteries. If you can find documentation by the manufacturer the DKL batteries are recommended, then they should be safe. Unless you know and really trust your vendor from past experience, I wouldn't go by what they say. They might not really know, and they aren't the one putting the mod up in their face. Historically these DKL batteries have been shipped and used in a number of Vamos, apparently even stacked. If it was me, I would go with a more known entity and use one of the more acknowledged name brand batteries in single mode. You can't go wrong with AW IMR's.