TIL massage for chronic neck/back pain can be FSA/HSA-eligible — has anyone actually done this?

A lot of us book "relaxation" massages that are really about desk-job neck or a cranky lower back. Turns out if it's an ongoing condition, massage can qualify as a medical expense payable with pre-tax FSA/HSA dollars (~20–30% effective discount) — but it needs a Letter of Medical Necessity from a clinician, and even then each session needs receipts tying it to the condition. Swiping your FSA card at a spa without that = you carry the audit risk.

Curious: has anyone here actually gotten an LMN for massage? Was it worth the hassle? And for those with FSA money expiring every year — would you bother, or is the paperwork a dealbreaker?