My first question is why would one need to borrow Weatherby data? It's not like there's a lack of published info on the 7 Rem. mag.
If you are absolutely determined to use more powder just use the old data with the highest charge weight you can find and have at it (I'm being facetious). In the older manuals I'm sure you will find loads for the Rem mag that match or well exceed current Weatherby data.
As many of our members of the 'Fire with friends in the industry and in ballistic labs have related many times, the old methods of "judging" pressure were just "WAG's". Newer instrumentation used for the last few decades is far more precise and that's why the loads have been adjusted downward over the years.
I have several Remington 7 mags and a Weatherby and all of my Remingtons would show "pressure signs" (ejector marks, etc.) well before reaching the loads of my Weatherby.
