A 1.5 kilo, I guess that be about 3lbs. So probably just half of the flat? Or maybe from a really tiny cow, haha! The rub I like for brisket is;
2tbsp black peppa
1tsp garlic powder
1 tsp onion powder
1tsp cayenne pepper powder
I also like to inject a brisket with a 50/50 mix of beef broth and red wine vinegar. As far as cooking time, I can't say, having never cooked a piece of brisket that small. I keep the smoker around 250 for brisket. When it gets to about 170 internal temp, wrap it in foil with some dark beer (stout or porter) and butter and beef broth. cook to 215, then put it in a cooler or wrap it in some towels to rest for an hour. As far as wood, I like mulberry or pecan, doesn't matter too much, whatever fruit, nut, or hardwood you have and you like.