I am the OP on this post and I'd like to thank EVERYONE who has taken the time to respond to my posts and questions. I have tried to be clear in my posts regarding my level of experience (i.e. somewhat experienced hiker but not veryy experienced in Yosemite and its rules --both written and unspoken) and my intentions, and I appreciate the opportunity to have a discussion on this forum so I can better understand the way that experienced and conscientious Yosemites use the Park and interact with each other (both on and off trail). I have found this and other Yose forums to be very informative and supportive! So thanks very much in particular to Geezer, Buster, JR and KevinD for your comments!
Regarding the issue of food caching, the consensus of the comments as I see it is 1) food caching is not expressly prohibited by Yosemite's rules and regulations, but 2) there seems to be a difference of opinion/understanding as to whether food caching is a proper and conscientious practice. Some view the practice of food caching to be totally OK and others view it to be allowed under the rules but an abuse/bending of the rules.
At the risk of sounding a bit defensive, I'd like to clarify that my question about food caching had nothing to do with avoiding/minimizing food weight. My concern was the capacity of our BV500 and how to plan rule-compliant food storage for all 6 days of the hike in the event everything didn't quite fit. A second cannister is obviously one solution, but my question about caching was inspired because I had seen an experienced Yosemite hiker suggest caching on another post and I wanted to start a more detailed discussion so I could better understand the practice.
I understand Buster's concerns about the potential impact of caching. I realize now that I didnt't skillfully articulate this in my original question but impact was one of my concerns and was one of the reasons why I posted the question. I know that there are 20 large boxes at the Tenaya Lake / Sunrise trailhead, only 2 standard boxes at GA, 2 large boxes at May Lake and 2 large boxes at Sunrise. I also knew that there are 18 large boxes at TM kiosk and 5 at TM backpacker camp. I also knew that there is no camping at Tenaya Lake, so there is no overnight camping use of the 10 large boxes. What I don't know is what is the actual use/capacity of the Tenaya lake boxes and whether capacity is an issue, especially in early Sept when we would be there. If the 10 Tenaya boxes are are often full, then yes I would see that caching there would be legal but inconsiderate, and in that case I definitely would not cache. If the 10 Tenaya boxes are always/usually mostly empty, and if caching is not prohibited, then it seems there is minimal potential impact and maybe caching would be something to at least think about. Either way, I dont have enough past experience at the Park to know these basic things, and that's why I love being able to ask questions and receive input on forums like this.
Also, unless I'm not understanding the rules, I don't quite understand how I would be using the boxes at May Lake or Sunrise HSC if my hike starts at GA and if I'm not caching at Tenaya YE03. If I start from GA and I am not caching at Tenaya then all of my food etc (except for my Day 1 food) must fit in the cannister on Day 1 for the whole trip and I wouldn't be using the May Lake or Sunrise boxes. Also, in terms of impact, I would not want to use the May Lake or Sunrise boxes anyway since there are only 2 boxes at those locations and, as a multi-day hiker mid-trip, I wouldn't want to impact anyone who was storing their Day 1 out-of-cannister food in those boxes. And if I am caching, then I would prefer to cache in one of the 10 Tenaya boxes (rather than using HSC boxes) so that during the entire trip all of my food is in cannister except for my Day 1 food at GA. Also, if I were caching at Tenaya, it is my understanding that I would NOT have any out-of-cannister food going up to Sunrise after the Tenaya cache resupply (i.e. the only 1-day out-of-cannister is from the Day 1 trailhead).
Anyway, this may have been much ado if all of our food other than the Day 1 food fits in the cannister, and, if not, then we may still rent the 2nd cannister, but I appreciate the opportunity to explore and better understand the full range of options, and, in any event, it seems my question brought to light a divergence of views regarding the propriety of caching, so maybe this gives others some food for thought (as it were) regarding this practice [?]