Why are you worried about reducing equity when all that amounts to right now is a bigger slice of zero? And if everything works out dreamily, the difference is whether you spend your days rolling around on a 12" stack of money or a 10" stack?
The reason not to bring in a third cofounder is that you don't have access to the right person...a cofounder is like your spouse only there's more money at stake and you spend more time together.
Finally, if you find the right cofounder, you can bootstrap, generate revenue and have better control over the terms at which others may be offered the opportunity to invest in your company. Having investors is not a goal, it is a means to an end, just like bringing in technical talent.
The reason not to bring in a third cofounder is that you don't have access to the right person...a cofounder is like your spouse only there's more money at stake and you spend more time together.
Finally, if you find the right cofounder, you can bootstrap, generate revenue and have better control over the terms at which others may be offered the opportunity to invest in your company. Having investors is not a goal, it is a means to an end, just like bringing in technical talent.
Good luck.