Although there are some well founded criticism against convertible notes, if they're insulted, the angels you've talked to are clearly behind the bandwagon. Paul Graham, arguably the most influential person in the world when it comes to seed financing, seems to have declared Convertible Notes the winning trend. Perhaps you need to educate your angels? Kindly of course.
I would gather that a hybrid isn't going to help you. Either the angels accept that you prefer a convertible note, or they don't. I don't see why they're going to accept a partially convertible note deal. In their eyes; it's either going to be a good thing (letting someone (ie. the VC's) that knows more about these deals, than you and the angels, set the price) or a bad thing (angels paying too much for your company stock).
Sensible angels will admit the former, while possibly leaning on the latter because it may be a better deal for them.
Having been through a run like this, I think it's about how to sell it to the angel investor. A pitch can basically boil down to this; "Look, neither we, nor you have a good sense of what the company value should be right now. Luckily for us both, there are professionals who do this every day. Let's see if we can get this ship off the ground together, and then down the line you guys get your money converted into stock at a rate that is fair for everyone. And you even get a rebate. Doesn't that sound great?"
Best of luck!
