I don't know what is up with the Recessive White's, but the few kits I have had born here were large as well. 67+ grams...
A recessive white male I had born in March was 68g at birth and he is now unfortunately only a little over 500g. I am going to try and use him with a few very large standard females I have that consistently produced kits in the low 50g range (with different sires). My hope in using these large girls is to produce some carriers that grow out larger, but hopefully bring down the birth weights to a more normal range. Like you mentioned, this could potentially be a major issue as we continue to work on this mutation, if not corrected. 104 grams is beyond huge!!! Kudos to the Dam...
I am very interested to see how this girl grows out, definitely keep us up to date.