Driving the tank hard? Yes.
Nearly to saturation? No.
The accutronics website gives a nominal drive of 3.5 amp-turns and (for the 8/10 ohm tanks) 124 turns on the driver transducer. This corresponds to a nominal drive current of 28.2mA (RMS, of course).
At 50mVac input to the Fender 6G15 circuit, it shows 19.8Vac output. Into a 7K load (the nominal impedance of that transformer) this is 2.82mA on the primary, which gets transformed to 82mA on the secondary (minus losses). This is about a 9dB overload. Accutronics gives the overload margins for all of their tanks except the 8/10 ohm (natch!) but if the vertical scale on their graph is linear in dB, then we can guess it's only about 5dB.
Furthermore, guitar signals can be larger than 50mV - (I need to measure them, though. I used to just take 100mV as a typical struck string, but I'm not sure that's accurate, even if it comes from R.G. Keen.) If you use a stompbox to drive the reverb, you may have levels well over 1Vac going in, which can make things very muddy indeed. However, it does have a dwell control that allows you to scale back the gain if the whole thing starts sounding like a belch in a bandstand.
That all said, it's the right sound, isn't it? I don't think anyone who likes reverb doesn't like Fender reverb (and if they don't, they're wrong, anyway). If that's the sound you like, clone away. Just be aware that you may be slapping that tank silly.
And Geek, I've been looking at those 9DX-based tubes (6JT8, 6EB8/6GN8, 6LY8, etc.) for a while now. My idea was to use four of them as outputs for a Leslie simulator (just need a quadrature generator for the volume controls!), but this is cool too
. Nice design. One note is that any transformer with a primary from 2K to 4K should work, which makes it easy to build from a junkbox. To use a 6EB8/6GN8 (which are common as dirt, it seems - that's the one I have, anyway) change the screen resistor to 4.7k 1W and the cathode resistor to 68 ohms.