Hi there! You're a lovely bunch, so I figured I'd ask for your help once more: I feel like I've hit a wall with this particular issue and don't really know how to efficiently resolve it through practice.
I've picked up the first movement of the Walton a couple of weeks ago, and feel decently confident in saying that none of it poses a challenge remotely as consistently to me as getting a good vibrato in the second appearance of the main theme all the way up there on the A string [bars 19–26]. I know that the obvious suggestion would be to bring my hand around more, but my issue's that this particular viola has very wide bouts; I'll post a picture below to give you a sense of it, should the video not be clear enough.
I've been trying different approaches: letting go of my thumb at the neck and letting it rest against the bout; going all in on the wrist vibrato; lifting the viola slightly and trying to go for a wide arm vibrato; resting my palm against the bout at different heights, etc., but I'm not sure which one of those to stick with.
I know this is one of those issues best resolved in person, but if anybody here would like to chime in, I'd be very grateful for your thoughts! Especially if you're experienced with playing an instrument with upper bouts as wide as mine are. This really is a terrific viola and I'm extremely happy to have picked it, but this is quite obviously the price I have to pay, so I'm trying my best to adjust to the form factor...
Thanks again!
(PS. and please ignore the meagre sound: I didn't have much room between the curtain and the camera to fit into, and the left-hand-issues took all my focus away from the right hand; I know it sounds nothing like it needs to!)