[eSteve]

kitcarkid,

the mounting of the seat/seat runners is not covered at all in 'the book', as you have noted, so we have all come up with different/similar solutions.

Here's what I did:

* 2 bits of left-over 19 x 19 each side between outer rail and tunnel rail
* Small plates on the top (so as I don't have to pierce the floor for the seat runner fastenings)

It will raise the seat marginally higher that Adrian's suggestion.