I'll try to help you understand my question a little better.
Rock Krawler has 2 different sets of adjustable rear control arms. A Flex set and an X Factor set. The difference is the x factor set moves the axle back 1". 1" isn't a huge deal, so we are not looking at a huge spread from factory length to moving the axle back 1". But in that distance, RK uses 2 different sets of arms and Kjeeper10 had to special order (at the time?) his arms to fall into the middle between factory length and 1" stretch. Which makes it appear that there is a void in the middle that RK's 2 different arms do not cover.
Factory Control arms:
Upper 17 1/2"
Lowers 19 3/4"
Rock Krawler recommended starting points for 3.5" lift:
Flex lower 19 1/2" 2dr /20" 4dr
X-factor upper 19 1/8" 2dr/ 18 9/16" 4dr (1 1/16"-1 5/8" longer than stock)
X-Factor lower 20 5/8" 2dr/ 21" 4dr (7/8"-1 1/4" longer than stock)
Looking at RK's starting points, they range from about factory length on the flex lowers to 7/8"- 1 1/4" longer on the X factor lowers and 1 1/16" - 1 5/8" longer on the x factor uppers.
Now look at the range of a couple other arms.
Upper Min 18"/ Max 19 5/8"
Lower Min 19 3/4"/ Max 21 3/4"
Upper Min 17 3/4"/ Max 19"
Lower Min 19 3/4"/ 21"
Both Synergy and Metalcloak basically covers that range with 1 set of arms and Rock Krawler uses 2. Both Synergy and Metalcloak can cover or all but cover RK's X factor 1" stretch starting points. They do cover kjeeper10's "custom" length "mid arms" so no need for a special order. Their recommended lengths are 1/2"-1" longer than factory with room to extend a little farther but short enough to be used with the factory settings.
Metalcloaks recommended arm lengths are:
Uppers 18 7/16" (15/16" longer than stock)
Lowers 20 7/16" (11/16" longer than stock)
Synergy recommended arm lengths are"
Uppers 18 1/2"- 18 3/4" (1"- 1 1/4" longer than stock)
Lowers 20 1/4" (1/2" longer that stock)
It appears that Synergy and Metalcloak are both capable of accomplishing with 1 set of arms what it takes Rock krawler to do with 2 different sets of arms. Rock Krawler's X factor arms may be capable of a little longer Max length (no body knows), but keeping the factory frame mounts will only allow around 1" "stretch" before you start running into clearance issues and coil bow which starts going beyond a simple bolt on lift (which all of these are). The recommended starting points for Rock Krawlers X-factor arms are only slightly longer so there's not a HUGE difference.
That's hillarious. You're the one with all the numbers making a big deal over a little bit of adustablilty and then make that statement. Bahahahahah!
So basically RK has offered the "Flex" lowers without a matching upper until just recently, leaving quite a few people (I'm sure) thinking they could add the upper arms later. Later comes and they order the upper arms only to find out that the arms included in their "upgradable" lift are too short to work with the off the shelf arms. So now/finally RK has a second set of uppers?
RK gives you 2 choices without any information to help you make an informed decision. No Min/Max length to compare to other choices/option(YES, there are MANY other choices). No Min/Max length to compare to their own 2 choices. Nothing to help you determine if the arms are going to fit your current needs AND be able to accommodate your future plans. Basically just saying here they are, trust us.
Are the shorter Flex arms capable of the same range that other arms like Synergy's and Metalcloak's are?
Is the small difference between the recommended starting point on the X factor arms and Synergy or Metalcloak arms really that big of a deal (maybe the X factor arms have more to offer than what it appears).
Maybe I'm just over thinking it and there's no reason to be aware of what your purchasing.