Hello Gav.
Driving slowly and in high gears and little strain in the engine - well done - and there's me thinking you were flooring it!, Sorry Gav. - I think you are doing the right thing, but don't let the engine labour in too high a gear even with low revs.
Adjudting it yourself? I wouldn't fiddle if it were mine. Bad for your case if you are going to progress this.
Kind regards,
Gareth.