Soaked red split lentils overnight for tadka dal. Proportion water to boil them in by weight? Any way to prevent the foam-up? (Ya know, these guys.)

So I rinsed 1 kg of them and soaked them overnight.

Haven't made them in a while,
and I've had some trouble in the past
with not adding enough water and having them stick quickly and cook slowly,
or adding too much water and having to cook them down for ages.

I'd just like a general "for ever 1 kg of lentils, start with 2 kg of water" or 2.5, or 3, or 4, or whatever it is.

(And like... time? heat? just a normal tall stove pot here.)

The other thing is, in the past, I've always had a problem with a mass of foam building up on top and boiling over.
Is there any way to prevent that? I've already rinsed them very thoroughly...
I cook red lentils in two ways: an excess of water and drain, or top up the water until they're done. In the latter case add any stock/wine etc. at the beginning, then top up with water from the kettle as necessary. This works for anything from lentil and tomato soup to dhal. It reduces foaming but doesn't eliminate it completely, turning the heat down to a low simmer and using a large pan are the best ways to prevent the foam escaping. I usually use a lid which helps a lot by reducing evaporation, but I tend to be quite a hands-on cook so topping up suits me. 

Red lentils don't need soaking, by the way (not that it does any harm).