PUN 1.66 - RPC & "synchronization" backwards compatibility

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In changelog of v1.66 it says:

Internal: Refactored RPCs and "Synchronization" updates to waste far less memory and perform better. For that, Hashtables were replaced with simpler object[]. This means, that this client version is completely incompatible with older ones.

We upgraded to v1.66, but we're really need the RPC to be backwards compatible with older versions. So can we just simply modify the code and change the object[] back to hashtables? Is there any risk doing that?

thank you!