hydraulic lifters and stiff springs
You are not looking at the whole picture.
Sure, the panty waist springs in a hydraulic lifter, at rest, are weak when compared to dual or triple valve springs, but that is not the end of the story. However, if you are using the correct, vendor recommended springs there should not be a functional problem - if you decide you want to use some 400lb open springs because your 'buddy' told you he was using them, then you might have a problem.
What makes hydraulic lifters work is.... wait for it - Hydraulics! Just as when you use a bottle jack to lift a 3 - 4,000 lb car, with very little effort. The hydraulic lifter uses oil pressure, tapped from oil galleys, to fill the lifter and hold it to the correct height. The spring is there mainly to keep things in place.
A lot of science goes into making an hydraulic lifter, especially the many variations that are the basis for high performance hydraulic lifters (anti-pumpup, variable duration, etc). When coupled with proper setup, careful adjustment, proper selection of oil viscosity and block preparation - hydraulic lifters can rev reliably to high 6,000 or low 7,000 rpm. Even if it sounds like more work than just dropping in a set of solid lifters - and it make you go through a little more mental gymnastics - still, personal opinion, hydraulics have an undeserved reputation as being easy and weak. To me, thats like saying you have a bad set of golf clubs or a crappy fishing rod - sometimes its not the tool that is the cause of the problem, it could just as easily be misapplication, wrong tool for the job, poor preparation lifter bores can wear-just like brake cylinders,valve stem passage; or the user really should have looked into roller lifters or solids for what he wanted that engine to do.
Its always funny when some guys only have one answer for lifters, solid lifters. Yet when they go fishing, hunting or work on the car - they have a whole box of different choices available to fit the correct lure, rifle, bow, bullet or arrow or tool to fit the job.