Hi! Seconding request for more info. Starting dose on Lantus is usually 1 unit or even .5 unit - you have to start low and go slow to find the right dose - work your way up every three days.
There is a weight based formula for starting dose that can be found in the Tilly Protocol:
initial dose = 0.25 x ideal weight in kilograms
If 15 lbs is Smudges "ideal" weight, based on that formula, his starting dose would be 1.5u. It would be helpful to have Smudges' spreadsheet if you had one.