SPC #18 which became SP #14 and SPC #21 which became SP # 17 were not deck-less, as were there sister class locos that went on to the SP and NWP. #14 and #17s odd appearance comes from there re-boilering and addition of lower steel cabs. Perhaps B. Norden or R. Hees have more information. It may be possible the SP may have extended the frame during re-boilering.
Dunscomb does not state that they were deck-less (at least in my copy of A Century of SP steam). I knew Guy Dunscomb, Dick Datin, Walt Stampli, and Dale Darney, having discussions with them about locos and rolling stock of the SP. None of them ever stated #14 or #17 were deckless at any time. On page 219 of Mac Gregors South Pacific Coast are photos of sister SPC #20 having had a derailment. In the photos you can tell it (as well as others in its class) was not deck-less.

Alan B