Hey Brian,
I know common sense tells you NOT to go negative on a property, if you can, but since we are in the real estate investing business, when did common sense ever make sense?!
Please take the preceding with a hint of sarcasm....But on to your question....Personally, I feel that you need to balance out the pro's and cons of (potentially) going negative on cash flow vs. the gains of pulling out equity.
First of all, using conventional lending, an underwriter may catch this fact and kick out your file. I'm not saying they will, but it is a possibility. Lenders are very suspect on income-ratios when it comes to investment properties. Just because your loan officer/mortgage banker says it fits guidelines doesn't mean the underwriters won't deny it. That's actually their job.
Second, although the rental market is hot, what is your comfort level (i.e. "reserves") when it comes to vacancies? Are you prepared to weather the storm? What about maintenance? Worse, what about unexpected personal losses not even related to real estate (job loss, health issues, catastrophic event, etc.)?
Again, you need to balance out your comfort level with the amount of risk you are willing to undertake. One major factor, I would think, is that the rental market is hot and should continue in this manner.
It sounds like you are in a great part of Houston - good jobs, in-demand properties, appreciating values, etc. This bodes well should you decide to pull the trigger and cash out the equity. Best of luck.