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I am considering several different scenarios:
1.) Flat max suggested spending level of $25 USD (seems to be the fairest option),
2.) Algorithmic matching based on SP with no preset spending limit (ie- minnows matched to minnows and whales matched to whales),
3.) Leaving it completely open (no spending limit) with completely random matching. Some minnows will gift to whales and some whales would gift to minnows (seems like the most interesting option.

As the project progresses I will probably open this up to Votes by my fellow Steemians and let you folk decide which way to go.

Num. 3 is the most interesting scenario indeed. Whales wouldn't be amused enough, though. But who knows? Maybe there are some minnows out there that are surprisingly wealthy.