I did one a few years ago for someone, and I wasn't a fan of the bigger tube in there. But, I was trying for a Swiss Army knife that did everything ok. It was setup for 6v6 with the bigger tube option. If I remember correctly, I'm thinking that it ended up perfect for a 6v6, the OT impedance works for a bigger tube. But the bias was all for a 6v6. Well, I feel like my 5f2a game is pretty dang stout these days, and I got the "more power" monkey on my back on a recent thread about a parallel SE build. So, I'm looking at a dedicated big bottle Tweed Princeton in a 5e3 sized cabinet. And I have a 5f2a chassis sitting here. And I have a 100mA power transformer that fits it. So, the cabinet is framed out, the board is punched, and I'm still waiting on a few more parts to float in. I modified the board layout more toward what I like these days. Just a couple things that make more sense to me. One is moving the bias resistor to the end of the board like a 5e3. I am making one big change though. I used the Princeton Reverb style NFB in my College Dropout I built a few months ago and loved it, and I noticed that the Blackface Champ used the same - 2700R with a 47R tail and a second gain stage. So, I'm doing the same, except just using the 5f2a tone knob instead of the B/T tone stack. Also will be putting a 2 option switch on the NFB. I have 5W dropping resistors on the way and 10W bias resistors just because that seemed an area of concern in most of the threads I researched. Speaking of bias, I will have a selection of 250R, 270R, 300R, 360R, 400R, 470R, and 500R resistors to choose from. I've seen everything from the lowest to highest listed and recommended online, so, since the resistors cost less then shipping, I went ahead and got a bundle to work with. Transformers will be Hammond 290AX 100mA 275v/325v PT, and the ClassicTone 15W OT with 5k/8k options. My plan is to bias it for max with a GZ34, then let the rectifier options (3A PT) be available to change the tone & feel instead of changing the power tube to 6v6. Any thoughts or input is welcomed, especially if it's from experience and will save me trouble down the road.