Looking for some "rule of thumb" factors for amp design project

[boodle]

Merry Christmas and Happy almost New Year to all,
I am in the process of putting together an amp design from various pre-existing designs to accomplish the following:
1. SE PA with the option of using either an EL34 or 6L6 to have SE PA behavior
2. Merlin's medium gain preamp to have a variety of gain setting available, will also use pedals
3. ~10W output is all I will ever need

Probable other design criteria:
4. Shooting for ~300V on the power tube plates to match an existing design
5. Possibility of adding an ECL84 driven transformer-less reverb after main design is finalized and tweeked
6. 10" speaker and a light pine cabinet [low weight is a desired outcome]
7. Using two 6N2P dual triodes for the preamp as an experiment with those tubes
8. To use negative feedback or not...

Don't have the full schematic sketched yet.

What I am looking for from the community:
1. Rule of Thumb design factors to help with PT selection
2. Merlin's medium gain uses 3 triodes, how to utilize the 4th triode?
3. Suggestions for tone stack selection/ shared experiences: Merlin's shows a Bandmaster B/T stack with his medium gain preamp, considering Merlin's Bone Ray stack with a Tilt and bridged-T controls also.  Any input on experience with the Bone Ray would be appreciated.

I have been researching PT's and I am narrowed down to a few possibilities:
Antek toroids:
1. 50VA - 240VAC or 220VAC tap @ 100ma
2. 100VA - 230VAC @440ma
3. 100VA - 250VAC @400ma
[Cost difference between these are long-run negligible, but if I can reduce weight without significant performance and longevity decline, that would be desired.]

Rule of Thumb factor's desired:
1. From my past use of an Antek 50VA - 200VAC transfomer in a PP design using ECL82's and SS bridge rectification, calculations would tell me that I would get 283Vdc post rectifier.  Actual loaded idle B+ was 254Vdc.  If this is typical, that would be a calculation factor of loaded voltage being 90% of unloaded calculated voltage.  Is that relatively typical or just an outcome of the actual design?

2. If the PA is an EL34, all 4 triodes are used, AND the ECL84 reverb is put in, the approximate current needed would be 116ma.  If I used the 50VA PT that is rated at 100ma, what would this overload tend to do: damage the PT, simply drop the B+ under those loads...what is a typical outcome or is the outcome too dependent on the actual design specification and can only be determined by actual experience?
[If a 6L6 is used, approximate current draw is about 10% under the 100ma for the 50VA rated PT.]

Other Q's:
1. How to use the 4th triode:  Will I need a recovery stage after the tone stack (at the end of Merlin's 3 gain stages) to be able to drive a 6L6 or EL34?
2. My understanding is that the Bone Ray and the Bandmaster could have about equal attenuation as some settings, so I'm sure how to factor that into the design.  Any experience with that and with the tonal differences? 
[Thinking the Bone Ray will be more flexible?]
3. How to implement a potentiometer-controlled negative feedback system or skip it all together?
[I tend to want minimum to zero NFB in general, but appreciate what it can do to low end management when volume increases.  I like a tight low end.]

That is plenty for now!!  Will post schematic when i get it completed.

Thanks for any and all help!

[pdf64]

4th triode could be recovery stage of an fx loop.
If there’s a NFB loop it’ll need to be a gain stage within that; NFB requires gain to do its thing, and generally needs more than the output valve alone can provide.
The only real alternative to that is use UL as local (rather than global) NFB, which requires an OT with a UL tap for the screen grid.
The screen grid could then be switched between the UL tap and a regular pentode feed from the HT supply, as NFB on/off modes. But a finer degree of control than that wouldn’t be easily achievable.

[boodle]

Thanks, pdf64. 
I like the recovery idea for the 4th triode.  It sounds like would also help me impliment NFB if I do so.

Anyone have experience with 6n2p vs 12ax7 in terms of distorted sound?

Looks like there are no "rules of thumb" for PT choice.  I will work on a proposed schematic and see if I get any hits.  Can anyone suggest an existing .sch file that has SE el34 and/or the Merlin Medium Gain preamp stage to get me part of the way there?

[boodle]

Starting a new thread with the schematic that has a title that is more fitting for what I need now.
Consider this one dead.