Breast Implant Size and Skin Tightening After Downsizing Surgery?

I would tend to agree with your assessment. I don't think 300 cc implants would make a significant difference if you feel the 350 are too large.
Decreasing down to 275cc is not a major size change (roughly 2.5 ounces). I believe your skin will contract down nicely to accomodate the new implant, given the relatively short time since they were placed .

It is certainly feasible to #downsize to smaller implants and also alter the positioning; if possible. However, decreasing is size may also require a Breast #Lift to to #tighten loose skin, better optimize the end result. Any #revision has risks of unhappy outcome or other complications. Also, the right implant for the revision is contingent on shape of body and your desired outcome.

Like all surgeons, I will say you need to be seen to make those types of decisions. Having said that, dropping to 275cc will make a noticeable difference. As far as skin recovery is concerned, it will depend on genetics and age, As long as the nipple is above the fold you will probably be happy.

It is very unfortunate that you will be undergoing another surgery in less than a year to resolve a problem that should not happen. Anyhow, I generally tell my patients that you need to decrease the size by about 100cc to really notice a difference.
Now, it all depends on how your skin quality was before surgery. If you had loose skin and the surgeon was trying to fill the skin up, you may have loose hanging skin after the fact, or your nipple/areola complex may be a bit on the low side. If the skin was tight before your surgery then it should not be a big issue.
Good luck.

Unfortunately there is no perfect method to predict in advance which size is going to be best in the long run. The problem with downsizing, as you have anticipated, relates to the skin being stretched and so it may need tightening. This would require a lift if that is the case. However, this isn't always needed, so your plastic surgeon should be able to give you some advice on that.
The other question relates to implant dimensions. It really doesn't need to be too complicated. First pick the size (volume) that you want, then the style (diameter and projection) will be determined according to the base diameter of your breasts. Again, this is something your surgeon should advise you on rather than you having to do it alone.