Thanks to both of you for your further thoughts.
Have already constructed 24" x 48" board, and measuring up available space again, I can increase width to 36" which will enable plenty of room for 2 or 3 curves at each end, but will have to stick with 48" length.
Still, enough room to make an interesting layout.
Thanks again
John

Thanks for sharing your solution to protecting trains from falling off track boards.

Thanks for this advice.
I see what you mean - it's better to build in a safety margin than take things to the limit.

Thanks for your info.
I was hoping to build track on a 24" x 48" board, so your experience of successfully running the 2-8-0 on an 11 inch curve means I should be OK.

I have recently purchased a number of N locomotives and rolling stock from an old friend who is moving from a house to a small apartment, and doesn't have room for his train set.
The locomotives are as follows:-
81159. 2-8-0 Consolidation Steam Loco, New York Central (approx. 5" length)
82758. GE EMD SD-45 Diesel, Union Pacific (approx. 4.5" length)
86060. GE DASH 8-40 CW Diesel, Santa Fe B/Y War Bonnet (approx. 4.5" length)
The track is Peco Streamline (flexible) with a number of turnouts.

My question is - what is minimum radius for locomotives to run on (I suspect that a larger radius required for the 2-8-0 than the Diesels?)