Dose - Gbl mixed results

[BuzzAldridge]

hi,
my uncles pet rabbit decided to try gbl, he searched this wonderful forum for info and found Mr G's level headed advice invaluable. 1st time he tried it 1.5ml it had little to no effect but after some further reading realised this was probably due to it being the 1st time and that a full meal had just been consumed before hand, he continued topping up but the desired effect wasn't reached.
next day the rabbit decided to try again on an empty stomach and upped the dose to 1.75ml as he's a 6'4 and 196 lbs, this did the trick and he was nicely bolloxed.
the following day he took 2ml on an empty stomach and had little to no effect and today took 2.2ml and felt the effects but not getting as high as 1.75 day. from reading i see that gbl doesn't really suffer from tollerance build up and regardless he isn't taking it long enough for this to be a problem anyway.
the rabbit asked if i could find out is he doing something wrong or is he just expecting too much from the substance or does he need to take more as he's quite a big fellow?
any assisance in this matter would be greatly apperciated