Right but if you dislike slightly undersized, couldn’t you have read the stats page and decided that it was too undersized for your tastes prior to buying it? 
You keep saying this like you had no idea, no way of knowing, somehow this yo-yo was forced upon you without your knowledge. Provided you knew you have a massive hate-on for slightly undersized (did you?) I don’t see how that could be the case.
Now, if you didn’t realize that preference until you added two of these to your collection and found out while playing them, that’s fine. I get that totally. You gotta try things to learn your preferences.* And to be honest, I’m with you: the Vayder is about the minimum size I’d even accept in a yo-yo these days. Anything smaller isn’t “mildly undersized”, but full on “undersized” 
It is true that the Vayder is slightly undersized compared to modern yo-yos, 100%, but I also expect that people know how to read yo-yo stats pages prior to making a purchase. Is this an unreasonable expectation? Should there be a special
BEWARE this is slightly undersized!
warning label on every yo-yo or something?
I’m not so sure about that; there are some very wide yo-yos out there which don’t have large diameters, and I do not think they’d feel “small”.
Unlikely, given the difference in material and very similar sizes. I guess if you actively dislike O / V hybrids and prefer more of a W?
One word of caution: if you have a massive hate-on for mildly undersized, DO NOT ever try a real undersized yo-yo (popstar, etc). I am quite mixed on these myself, the Ministar 2 is pretty decent but I always want to skew bigger like the Recess Snack and even then… ehhh.
* p.s. don’t marry your high school sweetheart for the same reason, kids!!
