Kenmore sells the STC for installing 206 middle seats in the rear of the C-180 and C-185 for $100.00. The STC does not include the C-170.
I called Kenmore last year and asked about using their STC on a C-170. They said, "The 170 is not included but the rear cockpit area is exactly the same size as the 180 so go ahead, it's ok with us if you can get an FAA inspector to sign it off."
Using the STC as a basis, my IA asked his FAA inspector if he would approve it and it was no problem. The installation was per the Kenmore STC except installed in a C-170. One additional structural angle p/n 0541130 same as 0742115-16 has to be installed under the floor on the bulkhead at the front side of the baggage compartment on land planes. Float planes already have the extra angle. Outer seat belt attach brackets p/n 0711084-15 and -16 have to be installed on the fuselage like on the C-185. Inboard seat belt attach points are co-located on bracket p/n 0711083-1 at the existing rear seat rear attach point in the middle of the floor. Kenmore sells the brackets. The tracks are standard Cessna p/n 0511000-14.
It is a very good mod. The seats fit perfectly and weigh 10lb each for a total of 20lb, 10lb LIGHTER than the stock seat. They can be removed and installed in about 30 seconds each, no log book entry is required for re-installation, and one seat or the other can be installed if only one seat is needed.
There are three different basic styles of 206 middle seats; short backed, small bottom utility seats that don't recline but fold flat and the full sized seats with either three-position recliners or infinite-position recliners.
In my opinion, the full size with three-position recliners are the preferred 206 middle seats. They are exactly the same size as the 206 front seats. They just have shorter frames which make the seats sit lower than the front. They are very comfortable, especially with headrests when reclining. BAS and Atlee seats don't recline. The hat rack shelf has to be removed to recline the 206 seats. When the seats are taken out, the seat belts make handy cargo tiedowns since they stay in the plane.
The biggest problem is finding a set of 206 middle seats to use. This STC has put a drain on their availability. Most places just laugh when you call. But if you have a set or know where to get a set, it's the best of the seat mods out there especially if you are concerned about your rear seat passenger's comfort. They are real Cessna seats and they give more leg room and comfort than Atlee's or BAS'. Depending on whether you want the utility or full size also makes a difference. I have seen prices anywhere from $100 each to $900 each with around $500 each being average.
If anybody has a set for sale, I'll take them.
C-206 aft (5th/6th) seats are not included in the STC. They sit too low to work well in C-170/180/185 installations and the seat track width is narrower than the 206 middle seats. Although the thought is tempting because there are lots of them available, I tried one out and it just doesn't work. You feel like you're sitting in a hole and your knees end up in your face.
C-210 middle seats are the same as C-206 middle seats except the track width is about a couple inches narrower than the C-206 seat's 12 1/4" track width. If you are getting approval on a 337 anyway and have a set of C-210 middle seats, the track width difference should not matter and is probably easier to install. I don't know what availability is on C-210 middle seats.
C-206 middle seat installed with a C-206 aft (5th/6th) seat for comparison. Note seat tracks.
