Tuna is best vaped with a simple little mod you can get at many department stores and hardware stores. I call mine "the grill". Most people recommend at least v3 or later versions.
V1 was called the "forest fire". Although it worked OK, there were a lot of reported accidents due to design flaw. Skeptics called it uncontrollable, unrestrained and dangerous. At best, the "forest fire" was kinda hit or miss. They were hard to find and if you happened upon one accidentally, you often wished you hadn't. However, even with all the drawbacks, v1 was the impetus for many technologies we use today.
The first officially upgraded version from v1 was v2, which was called the "campfire". Although this version addressed the hit or miss of the v1 as well as the unrestrained aspect, it still had it's own inherent dangers. In uneducated or irresponsible hands, the "campfire" was highly dangerous. If not properly used, it would often "short-circuit" and become a v1, or "forest fire". Additionally, v2 also suffered portability issues as well as ignition problems.
V3 is called "the grill" and addressed some of the portability issues of its predecessors and some safety issues. While improper use could result on danger, most of the dangers came in the ignition phase of use. V3 was powered by charcoal, which required a lengthy preheat and you had to refill the fuel between each use.
V4 is a simple upgrade of v3, and thus, it is also called "the grill". The primary difference in design is the use of propane instead of charcoal. This allowed much shorter preheat times and easier adjustment of the vaping temperature. You could also prefill it with a quantity of fuel that allowed many uses between refills, so that was easier too. The primary drawback to v4 is that purists tend to prefer the flavor that v3 created.
As a side note, many people do not realize that v1 and v2 also led to other PV mods, such as the oven and the stove, which eventually led to the microwave, toaster, and other mods, too.
In summary, when vaping tuna, I recommend "the grill", either v3 or v4. If you prefer, you can also use a different "brand", called "the smoker", but I have neither time nor inclination to get into that. V3 is certainly adequate and many argue that it produces the best flavor. In this product line, v4 is the quickest and easiest, although "the oven" is an OK mod, but I do not recommend "the microwave" for tuna as I think it does not deliver optimum vaping flavor for tuna.
P.S. Don't forget to get your tuna from a reputable company and make sure it is fresh. Old tuna tends to taste like ... well ... old tuna. Ideally, if you have the opportunity, harvest your own tuna for maximum freshness and minimal additives (hopefully).
I hope this info clears up the tuna vaping controversy. Maybe we can perhaps close the gate on TunaGate once and for all!