For clarity sake:
One should not remove and replace the data plate without understanding the rules governing that. It can get a little strange and I can assure you that there is a picture in the FSDO file of the data plate for that aircraft should an incident occur. The DAR and the FAA has taken pictures of every one we have done. 14 CFR part 43 and part 45
The Model IV 1050 gross to 1200 gross modification offered by DennyAerocraft and was done for float operations ONLY. Once floats were removed and returned the gear it did not apply and was once again a 1050. The equivalent of adding the 10-15 percent gross increase when on floats... very similar to what happens on many of the certified aircraft. This has been true to my personal knowledge since 1999. This does not apply to the Model 3.
There is no test data to substantiate this modification. We also have not been able to find any aircraft "DATA" to support the automatic increase of gross weight by 10-15 percent because it is put on floats.
The entry in the log book for the phase one completion should state the gross the V speeds were obtained.
The Weight and Balance sheet is required to have in the aircraft and should reflect the actual empty weight and balance with the gross weight. However, these can be (and have been) changed.
The Limitations, also required to have in the aircraft, may or may not have the gross weight shown as the phase one testing has not been accomplished.
So the log book will most likely be the bible... but if the data plate, log book and weight and balance sheet do not match it will raise questions.
Who will know?? maybe no one... but if there is an incident or accident the records will be looked at with more scrutiny by the FAA and certainly the insurance.
PS.. there is no requirement to have the gross weight on the data plate. But if it is you can bet it will be used.