[ctchocula]

Shorting your employer just in order to net out the overexposure seems putting the cart before the horse. Part of choosing who to work for is believing in the company's future financial outlook, because you are intentionally taking a long position in the company with your RSUs. Taking a short position both costs money and it would be simpler to take a long position in another company by choosing to work for them instead.

On the other hand, if you are 100% certain in your investment thesis that you don't want overexposure to any company including your employer, you could try direct indexing the rest of your portfolio e.g. buy S&P 500 except for your employer. Selling on vest is another simple alternative you could consider.