I found the answer in SNTP RFC 2030:
SNTP version 4 is designed to coexist with existing NTP and SNTP version 3 clients and servers, as well as the proposed version 4 clients and servers. When working with current and previous versions of NTP and SNTP, SNTP Version 4 does not require any changes; the protocol currently works or can be implemented specifically for NTP ir SNTP 4. For NTP or SNTP servers, NTP and SNTP clients do not differ from friend; NTP or SNTP client, NTP and SNTP servers are indistinguishable.
So yes, that will work.
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