Hell, yes!

alas, I suppose it wouldn't hurt.

Cheers   

OK - LET'S GET STARTED!

Well, almost. Before diving in, I need to lay out the usually disclaimers. Bottom line: Do not endeavor to perform this mod unless you know what you're doing. You assume full responsibility for any damage that may be caused by doing this. I'd consider this an intermediate level mod; it require basic rework skills. As with most tube amps, S7 is medium / high voltage, and poses a significant shock hazard if care is not taken. I'm happy to share what I've done, and am happy to support suitably skilled pirates with related answers. That offer of help does NOT extend to those without intermediate skills, or any further related or unrelated modifications.

Whew. OK. While the above needed to be said, I don't want to discourage those with suitable skills. The work is straightforward and the results are beneficial (IMO).

Step 1

Organize your workbench. You'll want to have the following handy:
* Soldering station. Tip of your choice - I use a suitably sized chisel tip.
* Soldering wick. A solder removal gun / pump can also be used, assuming it's able to access the rework area of the board.
* Necessary parts.
* Containers for screws you'll remove.
* Whatever else you need / use. I'm old, so I rely on a large, magnifying bench light.

Step 2

* Power down your S7. Let it sit for 5 / 10 minutes to be sure output caps have dissipated.
* Move to your workbench.
* Remove tubes. If you want / need to, take a photo or write notes indicating correct tube positions - if it matters.
* Remove the two side plates, placing screws in a container / wherever they're safe. Set the two side plates aside - don't want to scratch / damage them.
* Unscrew the top plate, placing screws in a container / wherever they're safe. Lift top gently; you'll have multiple connections to PCB from transformers, pot, etc.
* With S7 front towards you, tilt the top to the left and take photos / notes of the correct wire connections to the mother board. You'll need to assemble, so insure you know how to connect it back up.
* Before removing the top plate, remove the volume knob, and the potentiometer from the top plate. Place the knob and screws in a container. Take care not to scratch the top plate or knob.
* Tilt the top plate to the left again, and CAREFULLY remove the connectors from the PCB. There's a pressure tab on one side, but with a firm wiggle / pull motion, they'll slide off. Take note of the pressure tab; when reassembling, you'll want to be sure it's facing the inside of the connector.
* With Pot and connections removed, you should be able to lay the top on the left, face down. You may find it necessary to carefully cut some zip ties. Carefully - you don't want to cut into / nick the insolation of the wires being held by the zip ties.
* Now, you can remove the 4 screws that secure the PCB to the top plate. Place them into a container. You'll probably find a wire without a connector (green I think) that runs from the PCB to the power transformer. You can remove it if you like (if you do, take photos, make note of connect reconnection), but there's enough length to it that I was able to perform mods without removing it.
* Depending on any other capacitor mods you may have performed, you may need to remove flying wires for both interstage and output capacitors. You'll want to remove these; it's important for you to be able to flip the PCB front to back as you do the rework.

At this point, you have have the PCB loose and ready to work. Think about how you can work with it; if you still have wires running to the transformer, you'll need to work out how to perform your work next to, or on top of the S7 case. This is what I did - I covered the case / transformers with some clean work rags and laid the PCB on top. I was able to easily flip it as needed. If your PCB is 'free' of the amp, then work on it as you would any other board.

Step 4

1. You'll want to prepare your parts - specifically the capacitor and the Belleson regulator.
2. For the capacitor, you'll want to bend the leads in an arch, as to position them close to a 90deg angle.
3. Use some small diameter heatsink tubing to protect the leads. We'll likely not have any parts touching them, but it's good form.

Pretty nice of them to put Duelund caps in their amps without telling anybody 
This Nichicon thing seems a bit lost in this posh meeting   

That's just Anax's modified one.  Mine is modified with Jantzen caps.  This regulator mod does seem interesting though.