There are a couple of different risks here. One is that you pre-pay the company for more than the FMV ends up being; it sucks, especially with interest rates being as high as they are, but you'll get the money back with your tax return filed next year.
A different risk is that the price is spiked high at the moment the FMV is determined, and then falls before you're able to sell the stock. This would leave you with a short-term capital loss which you'd only be able to claim back at $3,000/year - https://www.irs.gov/taxtopics/tc409#:~:text=If%20your%20capi... - unless you have other short term capital gains in the same year to offset it against.
Has the stock been volatile since the IPO? How does the daily trading volume compare to the number of shares that will exit lockup on 3/15? If I were in your shoes that would inform my evaluation of the risk.