trussed roof convertion for loft

[dewalt7]

I am looking at converting my loft to an Attic room (i.e no building regs)which is trussed roof ("fink" type),i intend to construct parallel chords to replace the trussed roof supports but would like to know if these trussed chords can sit on the internal walls or blockwork has to be formed for the chords to sit on - If blockwork has to be formed i am assuming it would mean removing some of the internal wall below the ceiling in the rooms below as i only have approx 80mm from the top of the loft rafters to room ceilings below & cannot afford to lose much more height in the loft.
The chords would have a span of 5,4ME Gable to Gable & be approx 1,2ME in height.
Any advice would be appreciated thanks before i decide whether to proceed with the project.

[bd3cc]

For many reasons, seek professional advice!