Actually, it's not really a jump. It's flat. Remember, there's approx. 20% variance in any number due to the meter. So 212 + 42 = 170 to 256.
I really want to caution you against raising Jasper's dose based on pre-shot numbers. Lantus dosing is based on the lowest point of the cycle -- the nadir. You are also increasing his dose by 0.5u. It's quite possible that Jasper's numbers are low during the middle of the cycle and by increasing at the amount you have been using will put him over dose. Frankly, what you are doing could be dangerous.
We strongly recommend that you get at least 4 tests per day -- your pre-shot tests and at minimum, one spot check per cycle. Getting a curve on the weekends or at some point would also help.