How the new war matchmaking works and how to arrange war with a specific clan

Sorry about the long topic. We will explain two things in one post since they are related.

How new war matchup works
So each player in your clan carries a war weight. It's the available gold or elixir loot your EQUAL TH opponent can get from you. So in the following example, Bear weights 92K. Since the guy attacked him is also a TH10, there is no adjustment.

But if you look at Seb's, the available gold loot shows 63900. But the guy attacked him is TH10, so you need to add 10%, which is 7000 to his loot number. So 63900 + 7000 is roughly 70K, which is Seb's war weight.

After you obtain war weight for each player in your clan, you add all of them together and that's your clan war weight. 

What Supercell does is trying to find you a match that is close enough vertically and horizontally. Vertically means your total player war weight , aka , clan weight should be as close as possible. If no opponent is close to your clan weight while you are searching, you wait until you find one. They are also trying to match you horizontally, meaning our #3 Bear should get somebody who weights around 92K  and our #7 Seb should get someone who weights 70K ish. But this is where things can get tricky. Although Supercell TRIES to match you equally, sometimes, it doesn't happen. And you can tell when the war match is off a bit. Usually is when the opponent has bunch of rushed TH10 and since we have a lot of solid TH9, we get screwed. Cuz doesn't matter how you slice dice it, a max TH9 trying to take on just 1 inferno is tough. 

How to arrange a war with a specific clan

This has been done many times successfully, especially among the elite war clans. I know OneHive and Kara Heroes just did one on Oct 23. Reddit does that a lot. This is what you need to do to have an arranged war:

1. Know your player weight and clan weight. 
2. Work with your opponent's leader to balance out the weight vertically and horizontally yourself. So let's say we will do a 20 player war, it's better to pick equal amount of TH10, 9 and 8's with similar defenses. Then you find your player weight and add them together and try to stay within 100 points. 
3. You hit the button the same time. You will get matched unless someone identical to you is searching the same time, which is quite unlikely since you planned it out to be in such a small +/-margin, you should be matched. 

What contributes most to war weight

So the next question is .. does TH9.5 and TH8.5 make sense. Generally speaking, if the players are NOT adding any defenses but obtaining higher TH troops, then it is worth doing it. For example, I am TH9.5. I have 5 spells going on 230 troop space. My weight is 70K, lower than Seb's. So upgrading just a TH didn't seem to do any damage. 

I also saw some KC's players weight just 72K with max TH9 and lvl 30 heroes vs a 71K TH9 player with equal defenses but just lvl 16 heroes. That tells you heroes don't weight much in comparison to defenses. 

Then you look at infernos. Poker in our clan has war weight 86K, his defense is half TH9 half TH10, but he has infernos. That is 14K more than our max TH9!!! That tells you infernos weight a TON!!!! So is XBOW. Our Th8 player weights 48K vs TH9 are at least 64K. 

So defenses add weight, offense, not so much.