I don't think I would be able to share the diagrams. The book and drawing are both available for purchase. If you are on the fence, I would buy the Diagram of Tenders for SP. It's $55 and has hundreds of outlines of the various tenders up to 1950 with quite a few dimensions. Currently it is sold out, and if they are not doing reprints of it, my position may change on that. If you are set on a particular size, reach out to Arnold Menke waspman@cableone.net and he may have a larger drawing; he did contribute to the aforementioned book. That was only about $15, very reasonable if you ask me.
A 70 class tender comes out to be around 3 feet in 1.5" scale, which is similar to an Allen Models tender for a mogul/tenwheeler, I think. The trick with these tenders is the fuel bunker is the only flat place to sit. Unless you overhang a seat or straddle the pipe some way, it does put you very close to the cab. The downside I see of a larger tender is transportation may be an issue, since it will be closer to 5'.
In the end, pick the tender you like and think fits with the locomotive, you will find work arounds if it is the design you like.
