I am also interested in this. I had similar issues and got BSS. Been an eBay member for over 10 years. This holiday season I had an influx of buyers purchasing items on Dec 22nd-23rd, refusing to pay for overnight shipping, then leaving neg and low DSR. My listings even stated a cutoff date of Dec 22nd and overnight shipping in order to guarantee for Christmas.
Here is what I am doing. I have some free promotional items that I get from suppliers. I have tons of these laying around, so I've been listing them for a penny and my actual cost of shipping (shipping costs me $1.41, plus packing materials cost me around $0.30, so I charge $1.99). I'm basically breaking even, but it is a good way to build up my feedback and transaction count.
I also have these items in a fixed price listing for $0.99 BIN. So far its been working, but sometimes I will get a buyer complain. Even if I offer them a full refund and let them keep the item they complain. I had someone win one auction for a penny + $1.99 shipping. Mailed it same day. A few days later they bought another one for a penny and wanted me to refund them the money for shipping even though I sent theirs out days beforehand.
I've basically given up on eBay since even one low DSR or case will set you back far.
Here are some tips that I have which may help:
Item as described - I always describe items as being worse than they are. For instance, have some gently used items that I received also as promotional items. They are technically refurbished units but are essentially brand new, although some show more wear. I sell these for cheap, and in the description explain that the item WILL have scratches, scuffs, writing, dings, and other signs of use. When the buyer receives the item in like new condition, they are exceptionally impressed. If the buyer gets more than they expected they are likely to be happy. Kinda simple but it works.
Communication - This is another simple one, always be polite. I answer a lot of email from my phone so typically a buyer only needs to wait a matter of minutes or hours for a reply. They tend to like this. Also providing phone number can help sometimes. I have a phone line dedicated to my business which I keep with me at all times. Unfortunately people abuse this and think it is okay to call at all times of the night. At least I can keep the phone off, and have another line for my personal stuff.
Shipping time - eBay does not let buyers leave a low DSR if the item was delivered in the expected delivery date. My actual handling time is 24 hours and I stick to that very well. However, transit times are something I cannot control. eBay is generally off with their estimations. For instance, USPS First class DOES NOT take 2-3 days. To compensate, if I use USPS First Class, in the shipping options I select economy shipping (1-9 days I believe) and set my handling time to a few days to give myself some extra time incase the postal service takes longer than normal.
Shipping costs - Free if possible so that the buyer can't leave a low rating. If I do charge, I charge less than my actual costs. Buyers complain still, which can be quite troublesome. It is helpful to sometimes display the postage on the label (it is an option).
Cases - I always include a note with my items. It explains that customer satisfaction is very important, and explains how low DSR and cases hurt sellers. I mention that if they have any issue, to email me or give me a call and I will resolve the situation. This doesn't always work since most buyers are illiterate, but it can't hurt.