DIY in-car bike rack

When I got my new car, I specifically went for one that would be good for moving bikes around. I was also was fed up of bikes shifting around while I was driving, so I have created an internal bike rack. It takes up to 3 bikes with their front wheels off (although I could probably fit 4 if the handlebars didn't get in the way). The front wheel fits nicely in the door/footwell behind the bike (see 3rd photo).

Fundamentally it's a piece of aluminium extrusion – an aluminium bar with channels that act as mounting points for special t-shaped bolts. Then I've attached dummy hubs off ebay that attach to the fork. These dummy hubs have interchangeable end caps so they can accept QR or 12/15mm TA. All pretty cheap stuff off ebay, let me know if anyone wants links.

In the pictures attached, you can see it with one or two bikes attached. The car is a Peugeot Partner, and the seats are fully removable (you can see the 'spare' seat in the boot there, just in case). It's actually a pretty short car in the grand scheme of things, so with a longer estate car, van or SUV you might be able to do this just with seats folded up. This works really well with a car like this with a low boot sill and flat floor, but would work fine in others too.

My aim is to be able to carry the maximum number of complete bikes as seated passengers, with minimal disassembly – so far I've managed 3: two seats removed, two bikes in the rack, and then a third (front wheel still on) slotted down the middle. With this rack thing, the risk of the bike falling on a back row passenger while driving is greatly reduced – 3rd picture shows how much room they still have.

Really happy with this system, but there's a few tweaks it needs. It definitely needs 'feet' or some kind of fore/aft extension as it can roll forward a bit under braking (solved in this instance by putting the spare seat on it). Alternatively maybe some bungees to just hold the bike (this car has tie-down points in the boot). It also doesn't fit bikes with really long mudguards as the hub isn't high enough off the ground. It's an issue for the VO mudguards on my posh bike, but no problem for standard SKS type ones (like you can see on the dark green one pictured).