I had seen John (50) and Maria (40) in the '41 Census. Cannot find them in '51.
Given the rounding down that applied to the '41 Census, John could be between 50 (1791) and 54 (1787).
There is no other John Wood(Rackenford), other than 1795, that could "fit". I didn't extend the check to nearby parishes.
Maria could be between 40 (1801) and 44 (1797). The only Maria Slade I could see around this time was baptised March 4 1794 at Rose Ash, daughter of Roger and Ann (transcription). Looking at the original she was one of twins, baptised privately* Dec 19th and received into the Church March 4 179? - last character not clear. It has been transcribed as 4 - did wonder if it might be a 7. Need to check further..
Just a thought - If the 1841 Census entries are your John and Maria and the 1795 Rackenford John and 1794 Rose Ash Maria are the same, did wonder if the Enumerator might have rounded UP instead of down!! Needs more work.
mmmmmm?
* google "baptised privately" for an explanation