YO! you still haven't answered whether you have custom footbeds. if you don't, now is the time to find a skilled footbed molder near you -- and how near is going to be a function of reputation. I'd suggest PM to Arcmeister to find someone who can do this.
now, if you do already have footbeds, and want to try to do the boot mods yourself, I suppose you could try. I've skied in shells 1 size over before. Usually I've given up after losing a toenail or two. but here's how you can try to minimize the expense:
get to the Tognar website and get the following:
1) Bontex shims in both thicknesses, buy as many as you're comfortable with, I'd say at least 10 in each thickness but I'm a timesaver that way. at least 2 shims each thickness per boot for sure.
2) universal scissors
3) boot fitter's adhesive padding in 1/8 or 3/16 thickness, and I'd buy a piece about 24" x 24" or equivalent
go about using the Bontex shims one at a time, thinnest first, proceeding logically until you feel you have hit your vertical volume limit at the instep's lowest point on the shell. you can get creative here and use front-half-only shims if you really feel like there's too much vertical volume in the toe box. the point here is to eliminate the need to overtighten, which deforms the boot and makes it flex weird.
snug up the parts that feel loose by identifying where on the liner boot you're feeling insufficient security. cut the adhesive padding to mirror the spot... remember to orient the pad before you cut it, so that you're taking into account which side holds the adhesive. you can smooth the edges of the adhesive padding with an emery board (nail file) or similar abrasive. continue in this manner until you find the boot allows you to make desired moves without the foot moving excessively.
if you're going for the Lv II exam I'd suggest getting in lots of time making these boots work for you BEFORE skiing before an examiner. but that's just me, I'm not an instructor or coach...