Jig, I've got both fitted. I've added a set of Triton harnesses to my inertia reels by using the method Paul suggests above. I thought I'd not bother with the harness when nipping out for a quick run, but in reality only ever use the harnesses. This isn't safety based. With their fastenings, these isn't anywhere for them to go when I am in the seat. I'd imagined clipping them together behind the seat, but no. For road driving, I don't believe they are any more or less safe than the inertias, if correctly adjusted. If not correctly adjusted, they are considerably less safe, so they do mean a few extra seconds every time you drive. On the track, harnesses are a must. Unless you are tracking the car then, I'd think long and hard about the convenience of the inertias. Of course, having harnesses does also add to the theatre of taking a drive, they do feel a bit special, and passengers love them, so there is that to consider too. In terms of fitting, when re-using the existing fittings you just need to be careful about the length of bolts used for the outer lower fixing points. Too long, and they will punch through the outer skin. I measured the length of the bolt I removed, added the spacer length and bought a couple of suitable UNF bolts. I think mine were 7/16" and 1.5" threaded section, but yours might be different.