I got all of the mandrel bent tubing from Columbia River Mandrel Bending... mandrel-bends.com, they have a "builder's kit" option that gives a little discount if you buy a set of bends: 180's, 90's, and 45's.
The tight radius is mostly due to the fact that I'm using 3" for the cold pipe instead of 3.5" or 4" like most people.
The inside diameter of the HT4B outlet is 3" so I didn't see a point in going larger on the cold pipe, plus the fact that 3" is quite a bit cheaper.
I checked and it is possible to come straight out of the HT4B with a 90 and straight into the 180, however, this puts the 180 pretty close to the air filter (I only run a filter on the street, but I do want my filter to fit with ease since it gets installed and removed so frequently) and I'm running a large 6" inlet air filter so I decided to come out of the HT4B with a 45* and then a 90* over to the 180*.
The silicone parts are ordered so I should have a few pictures posted next weekend.