I've never heard of using aspirin, but I know of another method that contains no chemicals or any solutions, which it to off set the light pattern. so the last day of veg I usually turn the lights off for for anywhere up to 24-36 hrs. to reset the plants internal clock so it knows it's time to flower, when it receives the 1st day of 12/12 after the lights go off they'll stay off for 5.5 hrs. and then they go on for 1 hr. after that 1 hr period is up the lights go off again for another 5.5 hrs. bringing you back to when the lights stay on for it's 12 hr. light period, & if done for the 1st 2-3 weeks of flowering it'll produce male flowers on your female to pollinate and create your F1's
If kept healthy the seeds have given me a 95% germ and fem rate
The genetics I'm working with though are very impervious to many elements, so I've even had some F2's & F3's back crossed with some F1s to get even more stable genetics the 2nd a 3rd generations were just as stable as the F1's (surprisingly)