As this is a subject near and dear to me I will chime in. And for those of you that don’t know me, of the 409 instruments built so far, approximately 150 were arch top mandolins, 9 arch top guitars, and 11 were arch top ukulele. While I do not think that the skill level required to build a good arch top instrument is any greater than that required to build any other instrument, it is important to realize that arch top and flat top instruments are very different animals and produce sound in different ways. For sure, the amount of material and time necessary to build a quality arch top is significantly greater than that of a flat top. One very big difference between the two, is with an arch top, the back is an equal partner in sound production, with a flat top the back is much less important and its role less understood.
So, if you are considering having someone build you an arch top instrument, it is important that they have some experience with them and have a deep understanding of how they work. It is also a good idea for the customer to have an understanding of what to expect. The forte of an arch top instrument is to be loud, with less sustain than a flat top. The arch top guitar replaced the banjo in the big bands of the 1920’s because they could be heard through the horn section. When the guitar was electrified some years later, the production of arch top guitars went down significantly. They were saved when the jazz musicians of the time discovered they were more suitable for jazz than flat tops. It is an easy comparison to make when looking at steel string guitars. An excellent arch top will blow your socks off. I have heard three in my life that were magical. You would swear when listening to them that there had to be an amplifier involved somehow. When you start to get into nylon strings and nylon stringed ukulele, the difference gets hazier. Compared to a guitar the ukulele does not have a lot of sustain anyway. So the question becomes, is the time and extra materials needed to build an arch top ukulele justified for a small increase in volume. As a luthier I have found that building arch top ukulele to be a bit of a gamble. I have never had any of my mandolins returned but I have had two arch top ukulele sent back. I do not think that they were bad instruments, in fact I am happy to have them in my collection. But I feel considering the extra cost, the customers were expecting more or just did not bond with the instrument. Conversely, I have had a lot of success building for people who have had experience with and understand arch top instruments. I hope this provides some useful insight and feel free to ask any specific questions that come to mind.