This (and accompanying calculations) inspired me; I think we can improve the project selection criteria — specifically “target size”.
One of the points we clarified there is that the crowdmatching level we chose for alpha is arbitrary, and not very informed. We chose it because “$1 per 1000 patrons” makes for simple math & explanations, and because “it seems about right.” We fully intended to adjust it (and still do) depending on our real world findings.
I also mentioned how Snowdrift.coop itself has needed 4 years of buffer before we could begin receiving accumulated donations. That’s probably not sustainable for most projects.
edit: the core point, which the next paragraph is supposed to convey but (upon rereading) doesn’t, is this: we don’t have to calculate the best size project for our current rate. Instead, we can calculate the optimal rate for projects of different sizes, and then pick the projects with the highest rate as good candidates for bootstrapping.
I think we can calculate the optimal project size and crowdmatching rate using calculations similar to the ones in Does crowdmatching make sense?, if we also consider the creditcard minimum charge. I’ll write out a formula later, but the steps to write it should be something like:

What is the most we can expect the average patron to pay? ⇒ make this X

How much money does the project need? ⇒ make this Y
→ Calculate the target crowd size.
→ Calculate the crowdmatching rate.

How many months of pending donations can we tolerate? We do want projects to get the money, after all; if our time scale is years like it’s been for Snowdrift, cards are likely to expire and be forgotten, etc. ⇒ make this a constant in the formula so we don’t end up with a 3d graph
→ Calculate how many patrons are necessary to reach $3.79 within that time period (minimum sustainable crowd)
⇒ The optimal size project has a large enough user base to reach the target crowd size, and the smallest minimum sustainable crowd.
Keeping in mind that the “Project has to be important & known outside the FLO community” criteria — which push us towards larger projects — I think the curve will show a trade off where larger projects are ideal for lowering the perperson contribution, and smaller projects are ideal for reaching sustainable numbers sooner. So then we just need to actually decide on an amount perperson and choose the smallest projects which can satisfy that amount.
I didn’t know where this was headed when I started writing. It’s an interesting conclusion. I don’t have time to think about it more now; it’s really, really late and I need to get to bed. I’m interested to see what the dollar amounts look like, though!