Lifted off the cart slot, pressed the plastic circles attaching the expansion port to the N64 mobo and lifted the espansion port off the mobo with a screwdriver, as I did on page 1 of this guide.
I decided this time, as I will be soldering to the bottom side of the N64 mobo to connect wires from the cart slot connector to the cart pins, that rather than bend off the pins as before and soldering to their connections, it made more sense to reduce the size of these pins and solder directly to them (as the pins connect directly to the intended soldering points). This will give far stronger solder joints as there is more surface area to solder to.
Before I do this, I just removed the two pins which don't connect to anything (ie no pin holes under them):

I will reduce the pins height in the pic with wire snippers (or I could dremel, but clippers will be neater and easier).
One consideration I noticed is that the cart sits nice and flat with the cart slot connector on one side, but not quite on the other side. The raised bit is only the black plastic part not the metal part, so can be easily dremeled down to be flush with the cart if required. This might make it easier to make the cart holder solid.


The cart will have to stick out of the finished console so it is easy to get a cart in and out, however it only needs to stick out about 2.5cms for this; which is ideal, because by the time I mount the cart onto the back of the mobo I need 10cms for the controller and all its wiring - which I have nicely. I anticipate the final height of the console will be 19cms (with cart installed, otherwise it will be smaller); the width is likely to be 25.5cms (using the large speakers I intend to use) although I will try to reduce this to about 24cms if I can, the depth 6.5cms at the thickest part. Dimensions are including the casing. It will be interesting to see how accurate this prediction will be in the end.
More updates Monday - I will be snipping the pins, soldering wires to them and mounting the backing plate for the cart slot, and attaching the cart holder to the backing plate very securely. (time permitting).













