Absolutely, though that doesn't mean Carli is wrong for being conservative about that. Their recommendation for 2.5" is based on using aftermarket UCAs. I don't think anyone does the same level of testing and R&D that Carli does. Other manufacturers put out plenty of kits that stress out components. There is an acceptable range of stress people will make depending on their goals and budgets.
That being said, Carli is focused on off-road ability and ride, so they are more critical about those angles. If you are just using these kits to fit 35" tires, street driving & dirt roads, it's probably not a big deal. In that case, 3" is probably fine.
For example, the Readlift 3.5" kit seems to work for a lot of people, though it's a kit based on a top hat spacer and preload spacer on the same strut assembly utilizing the stock strut & spring, I would not recommend it for serious off-roading.
actually Carli's recommendation is more than geometry.
before i start, let me just warn readers that this will be a lengthy and technical post. Feel free to skip if you only want the look and don't care about ride quality.
ok you've been warned.
Carli recommend 2.5" because the King/ Fox they use are only 2-3" lift (depends on the spring rate used and preload adjustment) and you will NEVER want to max out your shock's potential when lifting. For instance, King/ Fox 2.5 has a max lift capacity of +3" (compare to stock). That means, to achieve that 3" lift you crank your collar down to show approximately 11-15 threads on top of the collar on the shock. That is not good because you're actually increasing your preload to get that "lifted" look by reducing the amount of distance your piston in the shock can travel to dampen the ride, and you're compressing the springs more.
Still not making sense to you? Think of it this way, your shock has a travel distance of position (p) 1-10 with the piston sitting at (p)5 when no preload adjustment is made (collar on top) with the +2" lift spring provided by the manufacturer. As your shock cycles, it goes from (p)5 to 10 for compression strokes and (p)5 to 1 for rebound strokes. This allows for a nice and comfortable ride whether you are going through Los Angeles crappy roads or through Mojave Desert or Baja doing 60MPH.
When you crank it up to get that 1 extra inch of lift, the piston sits at (p)7 and that's your new starting point. Your compression now go from (p)7 to 10 instead of (p)5 to 10, which makes your landing or going through bumps and what not harsher than it should be. In addition, your rebound now go from (p)7-1, which means it has more distance for your shock to decompress and slow down your shock cycle. Also not good for going through dips and stuff.
Unfortunately, that is how all these height adjustable shocks are designed. "Height adjustable" is not real but a marketing phrase used. Since adjusting "preload" yields the same visual result and using the term "height adjustable" is easier for average consumer without proper knowledge to buy their products.
That is why many people think their suspensions ride "firmer" or "more sporty" after adjusting the collar on their Bilstein shocks. It is not only Bilsteins are firmer (yes, their valving is slightly firmer than stock non ORG/ Rebel shocks, but that's beside the point here), but also because people are increasing the preload (reduce suspension travel) for that "lift"
So, Carli recommends no more than 2.5" not only because of geometry limitations, but also for shock performance. Majority of their customers buy their shock because they want to go fast in the desert, where bumps, dips, and everything in between come at you hard and fast. Applying what I just explained above, the more biased the shocks are, the harsher the ride will be in those situations. 2.5" is most likely the balancing point of visually appealing and performance, hence their recommendation.
If OP is going to use his truck for some high speed runs, I recommend skipping "height adjustable" Bilsteins and jump straight to King or FOX. But regardless how OP tackles his lift situation, I'd also put on aftermarket UCA as well just to bring front suspension geometry to where it should be.
How do I know these?
I go fast in the desert and I spend time with people who go even faster in the desert in their HD Dodge Trucks with their $10k+ suspensions. I've ran a set of Bilsteins so hard in the desert that they exploded and squired the shock oil everywhere when I took them off. I've also had enough harsh landings and jumped my vehicle a few times to know what a good set of off-the-shelf suspension should perform. I've explained this to many customers asking what's the benefit of getting King/ FOX over Bilsteins or other more "economical" brands. I've also installed/ uninstalled/ adjusted enough sets of suspensions on customers' trucks to know what's good and what's not. Finally, I've had enough customers who didn't believe me the first time I explained only to come back after going on a trip in the desert to tell me I was right and they are now paying me to remove their Bilsteins to put on a set of proper suspension.
