OK, some progress over the break. Also found some mistakes in the assembly. There were 2 cases where Matthew used the wrong connector type. For the programming header and I2C headers he used normal male headers instead of the stacking headers. We will have to unsolder and replace with the correct types.
Also I need to order a bunch of the stacking headers. Do you have part numbers? It looks like there are 4 types that are needed:
1x4
1x6
1x8
2x3
I have ordered the 1x6 and 1x8 from Sparkfun before for small builds, but the 1x4 and 2x3 are not available from Sparkfun. I would like to just add all of them to my next DigiKey order.
Finally, we have been using a genuine Arduino Mega for comparison, but the board is designed for the Seeeduino Mega which has different connectors. I am going to order a Seeeduino Mega from Amazon.com. It looks like it is missing a bunch of the connectors that the shield is designed to mate with. Did you have to install extra connectors on your Seeeduino Mega?
I believe the seeduino Mega always comes with the extra headers. However they are not installed.
For stackable headers, the are a pain. For 1x6 and 1x8 I ordered them from spark fun. For the 2x3 I got those from a stackable header kit that I think came from Nkc Electronics or Seeed Studio. As for the 1x4 I did not find them except fom China and you need to order lots. Same place that Sparkfun gets the others from. So for my prototype I simply cut a 1x6 …
Thanks for the reply. My Seeeduino Mega arrived without the extra headers . I contacted NKC and they say that Seeedstudio no longer ships with the extra headers, but they (NKC) have some sets so are shipping one to me .
As far as the prototype shield goes, I’ll see what I can piece together.
. I contacted NKC and they say that Seeedstudio no longer ships with the extra headers, but they (NKC) have some sets so are shipping one to me 
.