Hellwig 550 vs. Timbren for towing

I'm going to be towing a small Rv trailer (under 4k lbs) and I'd like to beef up the rear suspension a little. Both the Hellwig's and the Timbren's claim to level the vehicle under load without affecting the unloaded ride. From those of you who have tried either of these, or anything similar, what are your thoughts on them? Or is there something else I should consider?

note: this is a 2008 canadian trd sport doublecab with the 4 leaf rear suspension

 

I think either the Hellwig or Timbrens would be good for your application. Others may disagree. For myself, I would add a Addco rear anti-sway bar as well, $125. This will help during sidewinds and semi trucks pushing against you.

If you have an automatic transmission, be sure and have a transmission cooler.

 

I have timbrens on my truck (got TSB 4leaf done, because USDM trucks obviously don't need 4 leaves factory) They are basically a taller bump stop, instead of it picking up the weight when u get all the way through the over loads, they contact the frame sooner, supporting more of the weight.

I haven't really gotten too much chance to test them out, other than a super heavy landscape trailer, but if you load heavy (payload/tounge weight) she'll still squat like an indonesian