Okay, I can find my way into thumb position with little trouble at all now. I can even go up and down a few notes in tune. Given time, I can even reach the high D on the G string. The problem is that if I spend any amount of time up there, I find myself slipping and sliding ever so slightly that *BAM* -- my F# is suddenly ever so audibly out of tune when it was spot-on 3 notes ago. Are there any specific exercises I can do to prevent this and get more used to thumb position? I have the Simandl 1 and Evolving Bassist books, so if there's any specific exercises from those that y'all might favour, I could try them...or do I just need to keep doing my scales and arpeggios up there until I get more used to playing high?