If the company looks like an attractive investment, professional investors (i.e.: VC partners) will not let the drag on the cap table stop a deal from being done. Having said that, there are going to be three voices at the table when discussing this issue: yours, your co-founders, and the investor's. A big question is: do your co-founders feel the same way about your contribution as you do, or do they instead feel that "you got too much equity for the contribution you made". Note I'm not speculating about who is right and who is wrong, but if they feel that way, there are many ways they can cram your equity position down.

For example, they could arrange for a new company, newco, to be created and financed, and then to buy out the assets of the old company. All shareholders (including you) in the old company would receive some shares in newco, but it would be a much smaller percentage than any of you currently hold in the old company. But they will have arranged it so that they already hold a percentage of newco before the acquisition, as does the new investor. The result is that they end up with a larger percentage of newco than they used to have, and you end up with a smaller percentage. It turns out to be very hard to show that this kind of transaction is unfair, since newco brings a lot of new financing money to the table. Indeed, the other founders may feel that this is the fairest solution if they don't believe your contribution merited your current equity stake.

But if they feel really great about your contribution so far, the dominating question will be: Does the new investor feel that the ongoing management team is sufficiently compensated, and will they remain sufficiently compensated once future rounds of equity are incorporated into the cap table. If they feel that the answer to this question is "no", they will worry about having to dilute themselves later in order to properly compensate the ongoing management team. This is where the cap table drag concern comes in.

Sorry this is a bit complex, but hopefully I'm explaining it in a way that makes sense. In a nutshell, I'm saying that if your co-founders disagree with your assessment of the value of your contribution, there is a lot they can do to squeeze you out (or down) at the time of the financing. But if they agree with you, and if the company is really compelling, an investor will probably cope with the cap table, maybe by incorporating the future expected necessary dilution right now, by lowering the company's valuation.

Good luck with it. Too many unknowns to be definitive.

Dan