Mine runs well enough with the cone on a higher cam, but I do intend to get a box at some point. See how it goes with the cone....
May be worth printing off the guide and taking it to the garage doing the work, as the procedure is specific to this model (timing set at 2500rpm and sensors disconnected etc), and so it would be easy to have it done incorrectly by a mechanic that isnt familiar with the digifant system.