Be warned the wheelbase of the GS&W loco is 6'+7' 11"+6' for a total of 19' 11" while the wheelbase of the Lanky class 5 is significantly longer at 7' 10 1/2" + 8' 7" + 7' 10 1/2" for a total of 24ft 4", a discrepancy of 17.66mm in 00, that said if thats alright with you, Im sure you could make a nice facsimile of the Ivatt locos, as seen above
(incidentally Ive also checked the Lanky against the WLWR Lough Derg and the same problem arises)