Micro Brown Bassman-Princeton hybrid build

[cdemike]

After wrestling with some hum issues in an older build, I decided to just start over with a clean slate. The old amp is a 6G2 Princeton using an ECC99 push-pull output stage, but it was a really early build of mine and there are a whole host of grounding issues that I haven't been able to resolve, and I have been flirting with both a 6G6 Bassman build and the idea of a switchable harmonic/amplitude tremolo system; this seemed like a pretty good opportunity to tackle all the above. I didn't really love the ECC99 output section as a model for "big amp" sounds, since the triodes didn't seem to sound that similar to pentodes when driven, so I'm ditching them for a dual EF80 section inspired by Rob Robinette's mico amp series. The build is keeping one channel similar to a Brown Princeton, since it's my wife's amp mainly, and she really likes that circuit. The trem circuit is based off Steve Luckey's Trem-O-Nator circuit and uses the Supro-style oscillator for a wider range of speeds.

There are a few things I wanted to get a sanity check on before buying parts:
1. I'm not sure if the use of a transformer phase inverter is a good idea here. After thinking about ways to cut down on complexity, I realized that small audio transformers cost about the same as a single 12AX7, and I don't really want it distort anyway. Maybe it'd be better just to use another MOSFET since I'm already going down that road with a SS oscillator? It seems like the transformer helps cut down on overall complexity in the signal path, but this is my first time designing around an inter-stage transformer.
2. Putting the bridge rectifier on the heaters seems like it might allow me to elevate the heaters pretty easily while also providing a voltage source to drive the tremolo transformer (this build will not hum....). The old build I'm cannibalizing used an ANTEK toroidal PT which has no center tap on the filament winding, so I wanted to see if this would also eliminate the need for an artificial center tap. I currently have a humdinger pot installed, so no worries either way, but it seemed like this was a two-birds-one-stone situation unless I'm misunderstanding something.
3. I eliminated the third gain stage from the 6G6 design since the harmonic tremolo stage read to me like a repurposed LTPI, which I know adds some gain, albeit less than the unbypassed 100k/1.5k gain stage it would replace in both the 6G6 and 6G2. Because of the gain discrepancy, I adjusted the second gain stage of the Bassman channel to compensate and moved the treble control to follow the second stage rather than the third gain stage. I didn't see a reason why this would cause a major difference in the amp's sound, but there's a part of me that's wondering if I'm thinking about this too simplistically.
4. Because EF80s have much lower headroom than 6L6, I adjusted the grid resistors to be about 10% as large as in the original schematic thinking it'd get me close to scaling the signal so the output section sees a proportional signal as in the full-sized amp. 20k seemed to be right since Rob Robinette's site mentioned there should be a roughly 90% reduction in signal strength, and based what I've gathered from the EF80 datasheets that seems to be true. Really this last piece is to see if others have built with EF80s or similar small output tubes and have had success with other approaches or values.

Of course if there are any other red flags involved with the circuit as it stands now, I'm happy to hear it!