My car has daytime running lights and driver AND passenger airbags.
It is officially the safest car I have ever owned. (Insurance is cheaper than my wife's car....)
If it didn't have airbags, I might just consider having the baby seat in the passenger seat, but that still wouldn't allow for "the whole family" (dear God! I have a "family" now!?!?) to go places all together.
I got my photo software working again, so here's a few pics.
Yep, seat belts are designed to restrain people, even little tiny people in booster seats.
The "clicker" end of the seatbelts re-installed. When I originally put the battery box in, I made sure not to mess with the seat belt bolts, I simply unbolted the seatbelts to get them out of the way. No, the seatbelts don't rub on that metal edge. I added some rubber tube to cover that lip, and the seatbelts go over the top of the plywood cover.
I replaced the 1" thick insulation on the bottom with thinner insulation - in this case, a double layer of political sign. This makes the lid go on securely, without touching the battery terminals.
Here, you can see that angle-iron that I welded onto the ends of the battery box. I drilled a 5/16th hole in both, and painted it. You can also see pink insulation on two of the sides.
The plywood top bolts down with two carriage bolts - one on either side. The only unfinished piece is some sort of trim in front of the battery box, between the floor and the lid. I don't think I have the original seat anymore. I will look for it. Maybe I can make a trim piece from that if it's still around.