To make sure MAFS shareholders don't work together to stop an acquisition, any single stockholder, or stockholders acting as a "group," who controls more than 10 percent of the shares and votes against an acquisition, will be prohibited from converting more than 10 percent of their shares into cash.

The filing notes that the changes will make it easier for MAFS to finalize an acquisition, explaining that "we believe we have limited the ability of a small group of stockholders to unreasonably attempt to block a transaction which is favored by our other public stockholders."

A spokeswoman for Perelman declined to comment for this story, noting that MAFS is in its quiet period.

Confronted with the fact that SPAC investors have balked at several proposed mergers, sponsors see such loosening of restrictions as necessary to keep their SPAC from being greenmailed by hedge funds or other investors.

But Stanford's Jenter doesn't buy that argument. If a SPAC's investment team finds a good acquisition, he asks, "why wouldn't investors vote yes?" And even if there was a problem convincing some stockholders of the deal's merits, other investors would certainly see their folly and buy up shares in the open market.

Such restrictions on investor rights can raise serious questions about the sponsor's intentions, adds Donghang Zhang, an assistant professor of finance at the University of South Carolina who studies SPAC listings.

"It may not be the case that they used a technical loophole to avoid the regulations," he says. "But these deviations nevertheless are alarming in that the sponsors may find they can sell the deals without offering the protections."

The investor protections outlined in SPACs are of particular importance because sponsors face a host of potential conflicts. They are given wide latitude in choosing a deal, are sometimes allowed to buy companies in which they or their officers have an interest, and, perhaps most crucially, they can receive a big payoff whenever a deal is sealed, even if the company being bought is a bad fit, or was purchased at an inflated price.

An unhappy SPAC investor's main recourse in such cases is his ability to vote against a merger, or cash out his investment and walk away.

Service Acquisition Corp. International started life as a $7 stock. When it announced plans to purchase Jamba Juice, several institutions also ponied up $7.50 a share in a $200 million private placement to help cover what the SPACs original investors couldn't. Now Jamba Juice is barely holding at $2.75.

According to SPAC Analytics, a research firm, the annualized return for all SPACs that have completed an acquisition target since 2003 is a negative 1.4 percent, while those that end up being liquidated return a negative 2.3 percent. In an example of the premium paid for hope, SPACs that have yet to find a target have an annualized return of 1.7 percent.

A recent study by Vijay Jog and Chengye Sun, doctoral students at Ottawa-based Carleton University, put the chasm between management and investor in the SPAC universe in even greater relief.

Shareholders in the 62 blank-check I.P.O.'s they studied earned negative 3 percent annual returns, while management took home a whopping 1,900 percent annualized return.

The most recent MAFS filing makes clear the reason for such stark figures.

"Upon consummation of our offering, our sponsor will continue to exercise significant influence over us," it says, "and its interests in our business may be different than yours."