Wow what a project that'd be. Here's my thought. The only way I see this might possibly be done would be to move the IMA box back to where the recessed storage well is, cut out a whole lot of metal (some of which would likely be crash support) and you *might* have enough room for a small back seat. Problems with this, you put the high voltage stuff right where it would get hit in a crash. Then there'd also be the issue of back seat saftey in general.
A more expensive option would be to find a magic box out of a civic hybrid and see if you could get that to work in place of the Insight's magic box as it would be a lot more compact and give you more room for a rear seat. Doable?... Maybe. Would I? Nope.
It would be nice if Honda built an aluminum Civic. That is probably what a 4 place Insight would look like.
The Insight was really engineered from scratch for two. The wires for the IMA, the gas filler pipes, and venting for the IMA system go through the floor right where you would put a rear seat. The rear suspension would have to be redesigned for the approx.. 450 pounds of extra weight (2 passengers +weight of seats + extra structural reinforcing you would need due to structural issues with the seats and seat belts). Headroom would limit the rear seat to children, and there would be no room for their feet unless the front passengers were really tiny folk.
Back seat? Think "backward-facing rumble seat" ...Put the seat back facing the rear of the car, use the storage space for leg room... you'd have to be (a) a very small child, (b) a midget, or (3) a leprechaun... :wink: Or ride real slow in the parade, keep the hatch up, and have the stature-challenged passenger back there wave at the startled masses :shock: :shock: :shock: :shock: :shock: :shock: :shock: as you drive by and he/she throws candy at them
Everything has an engineering solution... but I think this is a lost cause.
It would be illegal to ride back there, not to mention uncomfortable, unsafe, a hazard to navigation, etc.... but I do like the idea of an aluminum Civic...
I doubt there is a way of seating more than two adults without going to a speciality shop that makes customized stretch limos - maybe. I've seen trucks, Accords, Volvos, VW Beetles as stretch limos. I'm doubtful these shops could do the Insight because it is short and does not use steel. If such a four-door Insight was built, the milage would probably be compromised to the point of being outperformed by the hybrid Civic and Prius.
My best idea would be a bubble hatchback. Even then, the drag would be increased, and the entry would be a problem.
I was attacked on an Insight Yahoo group for proposing this, but here goes. Adding a rear seat would be very expensive, and probably force you to make some serious compromises to the safety and possibly the structural integrity of the Insight. The only thing that I have thought of that would increase the passenger capacity of the Insight would be to remove the bucket seats and install a bench seat, increasing the passenger capacity from two to (a squeezed together) three. I have measured the bench seat from a Nash Metropolitan, and believe that it would JUST fit the Insight.
The drawbacks are:
1. Safety is compromised somewhat, the Metropolitan bench seat does not have headrests....which makes it more likely that you could sustain a neck injury in an accident.
2. It's undoubtedly illegal, though I doubt anyone would get caught for it. 3. You would still have to observe the passenger weight limitation as set out in the owner's manual by Honda.
4. The size of the Metropolitan seat base , and the presence of the Insight center console (I have a CVT, so I don't know how the 5spd. is) means the seat would have to be positioned in the far back position, in other words, this mod would only work for tall drivers.
5. The parking brake would have to be relocated, probably to one of those floor mounted "kick down" type parking brakes because the bench seat would cover the parking brakes old location.
6. You would have to make some mods to line up the bench seat with the insight mounting holes, though I don't think this part would be too difficult for someone who is a little mechanically inclined.
7. The third passenger (who sitis in the middle) would either have to share the passenger side floor space with the passenger on the far right, or, and I think this might be dangerous, straddle the center console, putting one leg on the driver side (which might interfere with driving) and one on the passenger side.
8. You would have to deal with seat belt relocation.
9. You would have to be sure not to block the vents for the battery.
Anyway, I haven't done this, but I may eventually. The final draw back is that it probably would affect your warranty, and this is my primary reason for not bothering with it yet.
If anyone else has any zany ideas about how to increase passenger capacity from two to three, I'd love to hear them.