the problem is that every pt has a different skill level with the three pokemon. my ivysaur is pretty mediocre, for example. it's hard to do matchup discussions without getting three people with different preferences in on the convo.
i've heard that you should DI the dthrow up, but it would seem to me like that'd just kill you vertically a little sooner...
regardless, i play very, very safe with my dthrow when i want to kill. it is squirtle's most important attack. ie never use it below a certain percent and always facing the closest boundary. assuming i'm not fatigued, squirtle should usually kill sonic below 150%. near the edge, the throw can kill at about 120%.
if i'm fatigued, then i just want to switch.
you know, if sonic tries to play near the middle of the stage, squirtle will have a tough time killing with dthrow...killing sonic is my biggest issue with squirtle here, but you can work around it by switching out early so that ivysaur can KO, or even switch to charizard for an even more potent killer.
55:45 is fine with me, 60:40 might be pushing it a bit. even 5:5 as is may be fine...although i think squirtle combined with ivysaur/charizard at the end of sonic's stock has the same effect as a 60:40 does...as could ivysaur at low percent (less comboable than zard) switched to zard after the mid point of the stock because ivysaur's biggest problem is not getting gimped. zard hardly has that problem.