I am in search of breeding quality platys. But have not had much luck getting many fry out of them. I think 10 is the most live fry out of any given platy and I have probablty 20 females that have had fry. Some even drop undeveloped embryos.

Are you removing the females or leaving them in the breeding tank? You might be causing premature births when/if you're moving them. There's nothing wrong with moving them, just try not to stress them when you do so.
Only a very small and very young Domestic Platy would have a normal brood as small as 10 fry.

Well for the most part I am leaving them in the tank as I have not been too successful at getting them into a different tank prior to. I have put them in breeder box a few times and that is when I realized several of them were dropping undeveloped embryos. Well I should say 2 out 3. One also gave birth to at least 15-20 live fry but they died. I think they were premature as the little yolk sak underneath them did not go away shortly after they were born like the others have. The problem with leaving them in my tank is survival rate. My fish LOVE to eat fry!!!

You could get some najas grass or hornwort to give them places to hide.

I might have to consider that. I do have artificial grass in almost 1/3 of the tank already and an undergravel filter. With some taller fake plants. I have heard the hornwart is good for that. I would ultimately like to put them in a separate tank when they get close, but I have to master that technique yet.

you can use almost any floating plant the ones I have used are hornwort, penny wort and water sprite. all of them work realy good becuse the fry swim to the top and all you have to do is push the plant down with the net and net the babies

I agree with Darrell, it sounds to me like they are giving birth prematurely due to stress. To avoid too much stress before they give birth I move the chosen female to a seperate tank a few days to a week after I noticed she has dropped. This way it gives her three weeks on average to adjust to her new setting before she is ready to drop again. I also remove the fry from the tank once the female has given birth and leave her in there for atleast one or two more drops.

I like to isolate the female when I see she is starting to grow round bellied with eggs(GENTLY).When stressed ,the female will often give birth to premature fry that have not completely absorbed the yolk sac..The Ideal time would be a week before she drops.Place her in a small tank,usually a 5 gallon tank is good.This serves two purposes:It prevents other fish from bothering her and also lessens the possibility of some of the babies being eaten.During their confinement ,the females are fed very well with live and frozen food,brine shrimp,grindle worms,frozen brine shrimp and dry foods.I like to set my drop tanks in the corner of my fish room where she will not be disturbed .I like to do a small water change every other day with aged tank water.I try to make the female feel comfortable and relaxed.After the young are born I transfer them to another 5 gallon tank,with a small Sponge filter with light airation.I start feeding them live Parammoecium,Mikro Worms,and Newly hatched brine shrimp.I feed them all they can eat.I make sure they get off to a good start.A combination of heavy feeding(not overfeeding)and frequent water changes will help your fish grow faster.

How many hiding places do you have for the females and what is your ratio of male to female? This could tell a lot about why your female are getting stressed out when you catch them.

Well it is a 75 gallon tank with many plants and there was a tall cave like decoration with many openings for them to hide in and several plants plus 1/4 of the tank was covered with low grass.

But tonight I did a rearranging of the tank. Took out the cave decoration and put in a lower tunnel with many different kinds of grasses attached to it ( it is actually PVC elbow). Added another corner with low grass and added a few bunches of hornwart. At this time over 50% of the tank has cover.

Female to male ratio is 2 or 3:1. I am also in the process of moving some of the extra males into another tank to see if that helps at all. I also added 2 more females today!