USE a powered HUB and see if it works.

Or unplug the power cord and leave the device plugged into the Pi.  See if the green and red lights blink.   Then go back to #1....

This time I will be making a case (most likely) out of acrylic sheets and metal rods to house Gridseed miners.
Dimensions will be similar to my first case as it will need to be mounted in a server rack.

Preliminary Dimensions
Length                       600mm
Width                        448mm
Height - Utility Shelf    133.35mm (5.25") 3U
       - Rod size            127mm (133.35 - 3.175 - 3.175 = 127)
Height - Miner Shelf        88.9mm (3.5") 2U
       - Rod size         85.725mm (88.9 - 3.175 = 85.725)
Holes                         97mm
Acrylic thickness          3.175mm (1/8" or 0.125")

Miner weight  0.9375 lbs x 20 = 18.75 lbs

Note: May reduce the rods length in the Utility Shelf section so the case can be removed without binding on adjacent rack equipment:  - 0.787mm (- 0.031")

Here is my inspiration:



Bottom level will be for power supply, USB hubs and controllers.

May quickly move from the supplied power supplies to a Corsair AX1200 (or AX1200i as I don't think their making the AX1200 anymore). This will require more space for the bottom level. Watching this thread for the required cables: https://bitcointalk.org/index.php?topic=74397.msg5492169#msg5492169

Top level will be for the Gridseed miners but unlike the picture I will have the fans blowing up. From here it can stack more levels depending on how much space the power supplies and accessories the bottom level can hold.

Looking at having a profession company cut the acrylic sheets.

Layout:

Red dots - location of the rods
Blue dot - main access hole for wires
Yellow dot - optional secondary access hole for wires (of course you can use any hole for miners or wires)

Picture of what I envision it looking like (wider with holes):

I want to work on some coins with POW/POS - is it best to use your repo - or use the one developed for NVC?

I think this is what you are looking for around line 53-55:

main.cpp:
/** Fees smaller than this (in satoshi) are considered zero fee (for transaction creation) */
int64_t CTransaction::nMinTxFee = 10000;  // Override with -mintxfee
/** Fees smaller than this (in satoshi) are considered zero fee (for relaying) */
int64_t CTransaction::nMinRelayTxFee = 1000;

Probably in  ~/.bitcoin/bitcoin.conf

Assuming I understood what you were asking.   :-)

The danger is like the guy who replied here

https://github.com/forrestv/p2pool/issues/183

You probably recognize him from irc. If he falls over to a backup pool then much later back to his own node, it might do nothing but HWs all day until he can manually fix it because of the 0 diff issue.

Part of the problem may be that python is an interpreted, not compiled language.

When you first connect to a new node and there are no stats at all you will get served DIFF 0 work which will cause HWs in some types of miners. If you mine for a while with any + it will get some stats stored, then you can disconnect and reconnect without the + and you should be fine, with vardiff giving you pseudoshare targets above 0. I just put in a suggestion to the p2pool repo that the minimum work ever served should be 1 (for sha256) or 1/X where X is the scrypt adjustment to the difficulty figure for that coin (it's in bitcoin/networks.py).