Yes go for it …jump in …. the water's fine 
Though I think 1 3/8" isn't any known gauge or scale … better work in metric where you have 32mm and 45mm gauge .
32mm folk I think mainly/usually model in 16mm/foot scale as if a two foot prototype except in NZ they model NZR which is 42" gauge and the scale is 9mm/ft. They are the rivet counters.
For what you think you want to do 45mm would likely be better where Gauge 1 work to 7mm/ft [as I was ear bashed by a P4 worker the other night when O gauge was discussed
]
Though personally I currently work to a loading gauge of 150mm x120mm which maybe 1/20 scale. Though have some models scratch built to half inch scale … they are NZR prototypes.
There are lots of people who model in all sorts of scales and gauges … that is Narrow Gauge modelling 
Been doing it for 35+ years now 
You could be interested in looking at IP Engineering who recently added a railbus thing to their catalog they supply lazer-cut kits which are nice to put together which wouldn't strain your body
.
Afterthought what about a quarter size RobRoy running on 45mm track, lpg fired with just as single central fire tube … bits from Roundhouse of Doncaster [ and others, Forest Classics etc ]
Edited By JC Uknz 1 on 19/02/2015 07:16:43
Edited By JC Uknz 1 on 19/02/2015 07:25:29