It's normal for this amp design.  The power amp section is very sensitive just like the preamp section. I find it best to just leave the master up all the way.  Of course, that's not practical if you want to get preamp distortion at bedroom levels. I've got a VVR circuit from http://www.skipzcircuits.com/Mini-Watt.html for this amp design.  I never ended up installing it though. I found that I basically only use this amp for cleans and run a pedal to get my distortion, which I can easily control with the preamp gain.  You want it? Email me @ tresspassor@gmail.com

I'd say to use a g12H30 if your stage volume is pretty loud.  Alnico for sure if you play it at less than ear piercing volume.  I tried several speakers and settled on a celestion blue.  It keeps the vox-like clean tone of the amp and distorts well at lower volumes.  BTW, this amp is a very conservative 15W.  The damn thing can get  louder than my 40 watters.

The paint I used is Krylon Fusion for plastic. 
http://www.krylon.com/products/fusion_for_plastic/

The letters were actually a bit hard to find.  I lucked out and found one type of stickers out of hundreds that would work.  You'd think it would be common since it's just standard times roman numeral caps font.  But most alpabet stickers seem to be in odd fonts.  Here's something I found on the web that could work.
http://www.stickersgalore.com/shop/theme/characters/subtheme/alphabet/121882

I just couldn't resist using the "muchless" pun for a faceplate on my Lightning amp cab.  The guys at SourMash built me the cab to matchless specs for $200.  It was pretty cheap and easy to make the faceplate. All you need is:
1. Translucent plastic. A  local plastics sign material dealer gave me some scraps for free.
2. Black plastic bonding spray paint from Home Depot.  $4
3. Bubble Buddies scrapbook letters from Hobby Lobby. $4
    Place on, paint over, and pull off for lighted logo.
4. Battery operated fluorescent utility lamp. $6
5. Wire and On/Off toggle switch.  I already had but readily available at you local Radio shackfor a few $.
6. Wood, plastic, or metal scraps to build the light box.
7. Imagination. Free

Nope.  I was wondering the same thing.  I had an idea to create a light box behind the logo.  There is room in that part of the chassis.  But I looked at how the screen print was done on the plastic faceplate and it's not really feasible.