OK as per Mika's request, here is how I would lay things out for casting. Mount your parts horizontally. You want as much surface area as possible on the uppermost faces so that as much resin and air movement as possible can be facilitated.
Glue some small gates right along the length of each of the walls and then glue that to a sprue:
- Sprue.png (10.38 KiB) Viewed 11455 times
Green is the parts
Blue is the gates
Red is the sprue
Don't have a single pour spout but rather leave the entire top of the sprue open. Make sure that the glue connection between the gates and the sprue is very weak so that once the silicone has cured you can snap the sprue away from the gates. From that stage you simply slice down the sides of the parts to remove them. Don't cut all the way to the bottom of the silicone and you have a split mould! The windows in the walls are no problem - just slice through the rubber when you get to there.
When casting, pour the resin into the sprue and then repeatedly squeeze the long sides of the mould. You'll see the air bubbling out of where the parts are and the resin flowing in to replace it. With a bit of squeezing and some luck you should be able to get rid of most of the bubbles. Try not to generate any lateral force when squeezing or you can affect the mould alignment.
Oh yeah I can make that....