Again, posted originally on P5's over 2 years ago. Cut and pasted here.
It is a bit jumbled up but you will get the idea.
[size=18]I have probably posted most of this stuff before, but I to make it easy, I am cutting and pasting from another site.
Ahrr the joys of having a machine shop to play with. :mrgreen:
My plan to convert the standard Mazda seats to be able to take harnesses (hopefully a first!) progresses. After much thinkingness a trip to B&Q yealed the plastic I wanted.
Then a bit of the turny stuff:
and Voila, 4 top hat flanges suitable for fixing through the seat back and creating a nice finish for the shoulder straps.
The idea is to cut straight through the seat the diameter of the socket shown. Push the apropriate length of 2 1/2" drain pipe inside the foam complete with some evostick to hold it in place then trim the shoulders on these little beauties so that they just meet in the middle.
Some evostick on the rear faces of the flange and carfully around the leather. Then some plastic cement of the parts, push them all together and jobs a goodun.
My aren't I clever? If only I had been smart enough to realise I would have needed 8 sockets, not just 4 for both seats! :oops:
Ok, for those of you will little else to do, you may remember I was thinking of modifying my car seats to accept harnesses.
So I decided to give it a go!
First off, remove the seat, always useful!
Saw the back off and commandeer the kitchen table and upset the woman of the house!
Ok, don't actually saw the back off!
Mark out where you want the harnesses to be. Shoulder height is always a good idea!
Get the knife out, say a prayer, #-o :( position the dog ready to kick and ...............
Then pretend you are in the Black Arm of the KKK, don't look like that, times have changed!
Then start cutting :twisted:
If you are having trouble, get an adult to help you.
That is quite a lump of ear wax!
Do the other side, oh it's so easy now!!!
DO a test fitting.
Add the glue, inhale deeply 
And bathe in the glory!
Test fit the other side.
Realise you need to trim some plastic and you need to saw straight, so get out the custom, purpose made jig!
Don't tell the Mrs that the tooth brushes are in danger of loosing their home! :|
Viola!!! He looks sad doesn't he?
The two halves just need clamping together while the glue dries.
