yeah i have done this and as furewolf has said you have to raise it to 50 in one sitting or else the server corrects it and adds the def point the next time you reload the mag from server side because you have to bank it on an odd feed of either antidote for power or antiparal for mind example: fresh mag i feed it 2 antidotes for a power one, banking at this point does nothing so no need to bother but if i bank it on the first anti fed or 3rd it will lower the points in the def lv bar by 1 untill its lv 10 because if i had to guess the server thinks any lv 10 mag needs to have 1 def point (could be wrong so no quoting that) but yeah you have to raise it to level 50 in one go as soon as you make it lv 10 because at 50 you can use monomates or fluids for pow/mind respectivly to start lowering the def bar for the next time you send its data to the server because this relies on client side bugs
another thing i have yet to test because it would efectively multiply the feeding time to lv 10 by 20 because if you bank after the first one you can essentially bank it after every single one to lower the def points bar by about 19 points because it takes 20 antis to get it to level 10 without def but as i said this is still untested (mostly because i hate feeding these mags because of the time you need and the feed rates)
but yeah most important things to consider when raising them are:
-bank on atleast 1 odd number feed such as 1,3,5,7 ect because of how the server handles odd numbers
-once its level 10 you can not change blocks, bank the mag, disconnect for any reason including logging out untill 50 and the def starts to go down
-read all feeding values on psoworld because one little mistake can make the difrence between a 0 def and 1 def stat point
-also check the specifics on the pbs you want if you dont feed using as a ranger to lv 10 for twins if you want it
-you should probably do this on a day off of work as this will take a long time possibly more than 24 hours depending on the feeding charts you use
-test how you will feed in the mag farm aplications(will have 1 def point in magfarm but thats okay because it wont ingame unless you log off ,dc or change blocks)
edit because i just noticed you said the trick doesnt work after using a cell : reason being why it showes that way to them is because of desynch but if you have them in your invin with the def bar that low you should be able to reload blocks at that point and have it saved as that