making sure you recover your investment
The miners only reach ROI if you are very optimistic about future events. Price will not go below 100, difficulty increase won't speed up further, and most importantly, the miners will be up and running in a month.
What I don't see is why you dismiss the option of refunding chip costs and the shipping fees. It's not like it costs you anything, you're not refunding the components you bought, you're not refunding any surplus you might've gotten for the chips. If there are people who want their miners despite the not exactly stellar odds, and it seems that there are, you can still do what others did and only ask for refund for one of the two orders, or combine orders with other group buys.
Really, the very least you could do is ask everyone what they want and act accordingly, since you're managing a group buy that's kind of what you should do as well.
I know bailing out is easy, making it work is the harder part, but if everyone bailed out at the first difficulty they had, we wouldn't be talking about Bitcoin... And i don't think we fight against "stellar odds". I'm very calculated and if i make a mistake, i'm also prepared to face the consequences. As far as i see now, 2.8 Terra hashes make their ROI in two months. I don't understand the anger behind the tone you used above. If you would like your chips, that's ok with me. But if you think about it, you could have BTC flowing in faster than you might get your miners and start mining. I gues i understand you too, having the miner in your hand, bragging about it and showing it off to everybody, but the end results are the same: you need the BTC that it produces. And this is what i offer here. I guess i can't make everybody happy, i'll just do my best to satisfy most of them.
PS: What you don't see is my work here. I know it's easy to dismiss it, but just think about the hours invested in this and then all of a sudden, it fades away to 37000 pointless views and 850 pointless posts in a forum, hm? How does that sound?