what wendy said! i think the 4.25 dose is working, but if he's only being tested at preshot, or not at all, i'd be worried he might get into lower numbers and no one be there to pull him up.
i think if he were mine and he's only going to be tested at preshot, I'd go to 3.5u and let him be a little higher while you're gone.
If your daughter can check him at preshot and again at +4 or so, and then follow up with more testing if it looks like he's headed into normal numbers, then maybe keep the dose the same or just reduce to 4.0u. I'd have her skip if he's below about 150 unless she's going to be able to follow up with more tests. When my son was kitty-sitting punkin for us, I had him text me with every preshot test and would give him directions about what I wanted him to do next.
He'll get back on track from a reduced dose when you return.
In any case, that gives you one option to consider.
Enjoy your weekend!