If you are modelling in HO all the OO products on Scalescenes.com can easily be resized down to HO scale (other scales see below).

If you are printing on to A4 or Letter, simply enter 87% into your printer's 'Scaling' options, this usually found in the 'Advanced', 'Properties' or 'Options' section of your print window. Consult your printers 'Help Index' for more details.

Other scales:

TT (1:120) - reduce OO by 63%
TT (3mm) - reduce OO by 75%
S - enlarge OO by 118%
Z - reduce N by 67%
N (1:160) - reduce N by 93%

All card thicknesses can remain as recommended in the instructions.

Happy modelling!