There are numerous reasons we went with a full 1 piece billet spindle. Obviously the con to it was cost vs a small extension blocks.. Taking into account all factors we found that a full 1 piece billet spindle was the only viable option to go for a production level kit.
Issue 1: Strength - The stock mountain spindles are rather weak and buckling the upper portion is not uncommon. With the increase in height below the lower a-arm we were creating an increase in leverage which would just increase the risk of failure in this zone, not something we were comfortable with. We spent a lot of time in the field and doing 3D modeling and stress analysis to ensure we had a part ready to handle the abuse of the customers.
Issue 2: Mating - The bottom "foot" on the cat spindle is cast and has a seam in the middle of it. This makes of a VERY inconsistent mating surface. This makes it very challenging to get a good mating surface.We ran some prototypes with extension blocks on the stock spindle just out of curiosity. They would be super tight fitting and very hard to install and then halfway through a day would wear in and have significant slop in them. Cats with extra steering system slop, not what anyone wants! lol There were some ways around it to get it to seat good but it became a lot more of a hokey DIY project then a nice bolt on solution.
In the end, our goal is always to provide the highest quality products.