Re: What about splitting the fuel line for a kicker.
There are a number or ways that you can do this.
You could install a three way valve (off, main engine, kicker) with a bulb on each of the lines that go to the engines. You could also have one bulb, located just ahead of the three way valve.
Another option is to have a fuel/water separator, with two lines running from the exit points. Once again, two bulbs downstream or one upstream of the filter would be fine.
You can also just use one line and move it form one motor to the other. You may have to construct an adapter to do this, since you are running different engine brands, but the method is workable.
Don't worry too much about bulb location. I've seen all sorts of comments about where they "must" be located, but have found in practical everyday use that it doesn't much matter where you put them.