I had a mandola custom built in China at 17”. When it arrived I pulled the frets, epoxied the fingerboard flat and refretted it multi scale and tuned it to Mandolin. So now the “E” is 16.5” and the “G” is 17.5” to get the “E” to work at a that length I needed .007 plain strings. See it in the photo. 

Big Muddy Mandolin has made several non traditional scale length mandolins. String gauge has to be adjusted to maintain standard tuning if the scale length deviates very much.

You could put custom strings on a mandola and capo 1 or 2.
A 17 inch mandola capoed at 3 would be 14 1/4 or so.

Thanks for the responses guys. I might try the 3rd fret capo idea as I have a mandola. Not sure if mando strings would be long enough though.

You may be right about mandolin strings being too short if your mandola is a UK version. If I understand correctly a mandola in Scotland would be called an Octave mandolin in the USA. Long loop end strings are available in many gauges. You might have to create your own set from individual banjo or bouzouki strings.

Thanks for all the responses, food for thought! I have discovered there is an instrument called a mandolele, which is basically a mandolin body but with a much wider neck. It s intended to be tuned lik a tenor guitar with the lower string pairs in octaves, but apparently could be strung and tuned as a mandolin? I have only found 2 makers who produce them, Ozark and Eastman. The nut width is 37 mm so would ease my fingering issues. The nut slots might be problematic if they are cut for octave pairs, so may have to get a new one cut? Tell me if I’m wrong!

This thread on Mandolin Cafe may be helpful.

mandolincafe.net/home/forum/ge...la-tuning

If the nut slot is too big just sprinkle some bicarbonate of soda and some super glue to fill the slot and then make a new slot.

Here is a boost for the idea mentioned on Mandolin Cafe. Follow Keith Richards lead and remove the low string (strings). The wide nut and long scale length of the Gold Tone F-10 look like something my big clumsy fingers would appreciate. Notice the adjustment of the string gauges to accommodate the long scale length. A new nut and bridge would be required.

goldtonemusicgroup.com/goldton...2KgxFpyzT

I will boost Big Muddy again too. Mike can adopt various neck configurations to his various body sizes. I am not sure if its the kind of work he wants to be doing. He has done it in the past and his prices are reasonable. Quite a few of his mandolins have made it across the pond.

Here is a shortcut to the F-10 video demo. The nut width of 1 1/2 inches would be very wide for a conversion to 4 courses. I am not enough of a player to know how that would work for 4 finger chords.

youtu.be/CFYlzWzkJvM?si=n4mkevsvzg7YjnAD

Tried 11 guage mandolin strings on a mandola with an 18” scale but the first 2 broke long before they reached pitch. (Simple physics - the longer the string, the greater tension needed to get it to a specific pitch - every day’s a school day). Maybe much lighter strings would do the job, I see someone above suggesting .007s for the E strings.

There are several interactive string tension calculators on the web. A contributor on Banjohangout shared a link to this one ,

chordgen.parmakis.co.uk/tensiontool.php

And from DAddario ,

daddario.com/string-tension-pr...7s0yrA2Sp