Hopping big beer and small beer.

[Deebee]

Following on from my thread regarding 2 beer from one mash another question springs to mind.
When designing the recipe you need to decide hops, amounts etc.
How would this be done in this case.
My thinking is to use beer smith to Work out the og of a 20 liter brew with big grain bill and hop accordingly.
Then sparge the remaining wort from themash and let it cool. I would them have a gravity and a rough idea of what the final strength would be. I could them use this to work out hops. How does this sound. It means that i would be able to make one on a friday and then the next on saturday when time is shorter.

Another question would be this. If i made a recipe of a 20 liter brew length with a grain bill of say 7000 g it would give me somewhere in the region og an OG 1085.

Seeing te grain bill is so large one could expec that there are a fair amount of fermentables still in the malt in the MT.

Is there any rule of thumb in regard s to what i could expect to get out f the MT aftrwards.

I guess the other way would be to do a no sparge on the initial big beer and keep the brew length short, and then dilute it as needed, but the qustion still remains as to what might be left.
Any thoughts? i don't mond experimenting, but would like a rough idea first.
thanks