I can try to help you out with shields, but your best bet is to figure out what you want and add it on and see what happens. I don't know the number limits on shields yet but their format seems to be similar to class mods, the main differences being the prefix and the manufacturer bonus. You can find lists of those at Link, and plug them in to a shield.
A cursory examination seems to suggest that the left side determines capacity, and the right side determines recharge rate. The manufacturer obviously determines the bonus listed in the text field, and the prefix obviously modifies whichever attribute you choose to add the prefix for.
The trick to making the manufacturer bonuses work is to enter the right manufacturer and number in the Material field (I.E., gd.shields.ManufacturerMaterials.Material_Anshin_3 under Material, and gd.shields.Title.Title_Anshin3_AmbushShield under Title for "Super Fast Recharge!" )
The prefix field seems relatively simple. Impenetrable, highest capacity, is "gd.shields.Prefix.Prefix_Max4_Impenetrable" Max4 refers to Max for Capacity, and 4 for the degree, and Impenetrable for the actual prefix. These and matches up in the table on the link above, just get the count right. I'm not sure what you'd replace "Max" with if you'd choose to use something else, though, but you can go search through med machines to find something similar to what you want and see how it's named. There also may or may not be letters involved as with "y" in the class mods.
This is a pretty good basis to start from though if you want to try shield modding.
I haven't tried this one out but I'll post up a shield that should work, if it doesn't or if you want a different pretfix/title, just say so or use my advice to change it yourself.
This should end up being a max-level Impenetrable + Pangolin for highest capacity. If you want recharge title, change Pangolin to Anshin in all instances and change Fortified to Ambush. I'm not sure what you'd replace Max with to change Impenetrable to Alacritous, though, and without the matching pair it may not have high enough recharge to be worth choosing over capacity. You can use any of the other titles too from the Shield page of the wiki, it's pretty easy to figure out once you do it a few times.