CSPA opt-out of F2B - F1 conversion

[wemoloh]

Just wondering if anybody here has recently (2019) successfully opted-out of the automatic conversion from F2B to F1 when the petitioner naturalizes. The most recent posts I can find are from 2015 (here) and describe a very awkward process of contacting both USCIS and NVC with ad-hoc letters requesting the opt-out.

There is conflicting advice on the USCIS and State Dept. websites. USCIS says:

If you want to opt out of the automatic conversion, you must submit a written request to the USCIS office that approved your Form I-130.

Whereas State Dept. says:

Applicants whose case is at NVC should submit requests using NVC's online inquiry form. NVC will forward the request to USCIS and change the visa category back to F2B upon receipt of USCIS's approval.

Whereas the above-linked thread indicates that the petitioner must contact their local USCIS field office.

So here are my questions:

• Whom do we contact first, USCIS or NVC?
• If USCIS, where/how to we submit this letter? What if there's no field office in the beneficiary's country? (In our case, the country is Jamaica, the nearest office is in Haiti, travel there is impossible, and international mail is slow and unreliable.)
• How will they respond: snail mail, email? Is there any way to have them communicate with the petitioner, who lives in the U.S. and has better postal/internet service?
• How long does this process take? Right now F1 is lagging behind F2B by almost a year, and we're wondering if it's worth it to go through this uncertain opt-out process in order to speed up the visa by a few months.

[wemoloh]

(Edited to fix characters in the quotes I copied from the State Dept website that were causing the forum software to truncate the post.)