I picked up a pack of these at the gun show today and got them on the 30s no problem.  In the instructions it mentions that you can install these on 20 rounders with some modification.  Has anyone done this?  If so, what modifications were needed and can you post pics.

I never used Ranger plates, but the modifications required on 20rd straight mags would be to pull off that metal "spring" that is riveted to the mag body with 3 rivets.

Break the rivets (its very easy to do - had it happen on a brand spanking new LEO marked 20rd mag) and pull out the metal "spring" plate. Now you can use 30rd followers and 30rd floorplates.

I have done this on two types of 20s, the older straight type and the newer curved type.  

The newer curved type (i.e., Bushmaster) were just as easy as installing them on a 30 rounder.

The straight type (i.e., Colt) with the angled base and metal follower required some work with my Dremel to make them fit.  The process is as follows (btw, I did this without any other references, so others who may chime in may have easier methods for, lets say, removal of the spring clip which holds the old base plate on):

-I removed the baseplate and follower spring

-I tried to remove just the spring tab that retains the baseplate, but I popped it out of one of the little rivets which held it in place, so I ended up having to remove the entire metal strip and the other little rivets which run from the top of the mag down to the bottom.  Hopefully there is an easier way of performing this step.  This allowed me to free the follower and easily remove any metal shavings created in the next step.
 
*The Ranger plate will fit fine on the front baseplate retaining tabs, but the rear tabs need to have some metal removed from the back of them to allow the Ranger Plate to fit far enough forward for the locking plate to seat and secure the whole assembly.  

-I began by sliding the front Ranger Plate tab slots into the front magazine baseplate tabs and allowing the plate to rest on top of the rear magazine baseplate tabs.  With a marking tool I marked the location on the rear magazine tabs where the rear ranger plate tab slot terminated (easily identified where the rubber overmolding meets the slot).

-With the Dremel and a disk/mandrel type cutter I removed the material from the back of the rear magazine tab to the marked line created in the previous step (approximately 1/8" of material from each tab).  NOTE: Obviously one needs to take all the necessary safety precautions such as eye protection and not be on any drugs or booze or be in the middle of doing something else which may cause you to draw blood or loose valuable appendages/organs, etc.!!!

-Then do a full test fit of the Ranger Plate and make any additional minor adjustments to the magazine tabs so that the plate seats correctly

-clean any metal from the inside of the mag body, then re-assemble

-To help seat the lock plate to the Ranger Plate after assembly, load up the magazine with rounds which will increase the spring pressure and help the locking plate to seat fully.  BTW, you will only be able to load 18 or 19 rounds with the Ranger Plate installed.

thanks guys