First of all, this thread did inspire me so please read this one first :
How clash of clan war matchmaking works
1. How a clan's strength is calculated
I suspect rather giving a clan one number to indicate its strength, it probably has multiple numbers in each category, such as troop strength, defense strength, spell strength, hero strength, army camp size, etc.. A number and range is assigned to each category and then normalized through geometric mean calculation.A geometric mean is often used when comparing different items and finding a single "figure of merit" for these items since each item has multiple properties that have different numeric ranges. For example, the geometric mean can give a meaningful "average" to compare two clans which are each rated at 0 to 100 for their troop strength, and are rated at 0 to 1000 for their base strength. If a numeric mean is used to calculate the ave strength, then the shifting of base strength will overshadow the troop strength. Using geometric mean basically takes the 'weight' out of the calculation and gives a more clear picture of a clan's overall strength from all aspects.
I also believe SuperCell gives Townhall level a different weight. I agree with what this forum says that a rushed fresh TH9 will weight more than a max TH8. That explains why our clan that barely has 5 TH10 got matched up with some clans that have 20 TH10. But when you look at their TH10 bases, they were super rushed.
2. How the search is conducted
So if Super Steve says "mis match is better than no match", I most definitely agree with the speculation that the longer you search, the greater chance the mis match will happen.See the above forum thread for more explanation. But in short, if the system can't find you a close ranged match, it will expand the circle of search and the chances of your clan being matched with someone significantly weaker or stronger will increase.
Another factor that matters in search is the pool of available opponents that share the close range of strength with your clan. Majority of the clans out there have just a handful of TH10, 10-15 TH9, 10-15 TH8 and rest with baby bases. The bases and troops strength are also spread in wide range with some maxed and some rushed. So if your clan is so strong and so out of the normal pool of ranges, you will have much less opponents to choose from, thus the chance of being mis matched simply increases because there aren't many available choices available so you must go out of your range.
3. How to build a war clan to get fair balanced matches
I believe SuperCell does a good job calculating and comparing clans' strength. The mis-match doesn't happen during the calculation, the mis-match happens during the search.
So based on the above speculated theories, here are my guidelines as how to build a successful clan for war:
1. Stay in the normal range of strength and don't become an elite clan unless you are ready. You will have much larger pool of clans to be paired with.
2. Recruit solid TH9,TH10 and TH8 and avoid rushed or fresh bases. That's because max TH8 still gets a smaller weight than a rushed TH9. But if your max TH8 player is a better fighter and base is harder to be crushed, might as well stick with a lower number which brings down your overall strength than having a higher TH player. Rushed TH10 definitely will hurt your clan more than having rushed TH9 or TH8 so choose your TH10 bases wisely.
3. Throwing 1,2 low bases will not help. But throwing 10 will. This is especially true for our clan while we have solid 30 fighters and that's all we need to win war. The bottom 15 players's contribution will be bringing our "strength" down to a good range while we have the top 30 fighting the war. As you can see from the calculation algorithm, 1,2 low bases won't help much, but once you throw in a large number, it will.
4. This is the most important factor : re-search after a few mins, so you stay in your range. This is more important than balancing your clan bases. So cancel the search and re-do it every 5-7 mins.
Good luck!
