Tim Phillips in the UK makes lovely 5-string fiddles (smaller) and violas (larger) - as played by Jackie Oates until some low-life stole it (has she got it back, does anyone know?). I had a nice 5-string fiddle made from a long-bodied Dolling strad by Shay Allen - now in the much more capable hads of Tania Opland in Alaska. Always a compromise, but if you're wanting to both accompany songs and lead tunes (specially back-to-back) it saves carrying two instruments around, or doing a quick change. Low F#'s a bit of a stretch though!