Honestly if you were to build your own I would do more than build arms. I would move the rear diff back to take some angle out of the rear cv's and also gain more wheelbase. If you simply want to make the machine wider and get a little more travel I would just buy a HCR or LSR kit. I like HCRs boxed arms better though.
Also if you build long travel I'd be willing to lend a hand with your spring rates and valving if you continue to use the factory Fox shocks.
If i build my own i would move the diff back an extend the wheels base. Not sure if i will use the fox shocks or not. Thank you tho i will let you know. The main reason i made this post was to see if people were that happy with the bolt on stuff. The more i think about it building my own would probly be best so i could move the diff back. It just all comes down to time line and if im willing to give up a few races this year. There must not be many hcr kits out there for no one to have chimed in.
We run a HCR kit on our Race Maverick... over a dozen sets have been sold, just don't know of any of those guys are on this site- so... yes you can build your own.. We have looked pretty hard at how to extend the diff back like we did on our Commander- just don't see how we can get by the axles hitting the rear arms- supposedly its been done but not seen any good pics yet. What you will pick up with a HCR kit is obviously 8 inches of more width..and 3 more of wheelbase (2 forward and 1 back) as well as more useable wheel travel. the biggest reason in our book is the durability- although the factory suspension on the Mav is a world better than the Commander was, it wont hold up for what we do...a few have tried and failed miserably. I'd only go with a Box arma but other don't and have done okay so far.
There is quite a bit of engineering that goes into creating a long travel suspension. It is not just about expanding the length and width of the trailing/A-Arms. If you dont have the fabrication experience it can be far more trouble than its worth. It is by all means possible, but you need to ask yourself if the additional headache and time consumed is worth the trouble, or is it just easier to buy a proven kit from HCR or another vendor. I have been designing and building off-road cars for years. Even with my ability to design and fabricate suspension systems, I still have my suspension components done by those that do them on a daily basis. The suspension is the one item of a car that I want done perfect. A mistake in the geometry which can make a car unstable, or a part failure at high speed will ruin your day and possibly more than that.
As much as I agree with your logic, I have to disagree at the same time. I bought an aftermarket suspension for my Commander and still had to put many hours and more money into it to make it work. I am not the only one with this experience. It is also not just one manufacture. So it's a double edged sword. You spend a lot of time and money making your one more than once to get it right or spend big bucks to buy something and have to modify it to make it right! Don't shoot the messenger just sharing mine a few others experience's.