Nigel Burbidge
I also converted an N7 to EM using the Gibson wheels designed for the Hornby J15 and it was one of the easiest loco conversions I have carried out. Although I usually use a GW Models quartering jig it is entirely possible to get the quartering right by looking through both wheels once they are on the axle and lining up the spokes (16 spokes to a wheel) – I only know because on one occasion I couldn’t find the jig and used said method with perfectly satisfactory results.