The Onega cooler for skelestruder is a better solution. I recommend that route.
UPDATE 11/02/18: added STEP file for folks to play with
UPDATE 9/08/18: This is not really compatible with the new R3 cage from Prusa. I am not planning to address that since I have moved on to Skelestruder. I will leave this up for folks to derive.
UPDATE 6/30/18: It was brought to my attention that the newer MK3 beds are shipping with screw terminals, which is better in many ways. But the screws are much taller than the previous solder connections so the low profile cover will not fit over those. Thanks to Shrikestorm for confirming that replacing the socket head screws with button head will fit. Also looks like you need to trim the plastic on the terminals. So you need to replace those two screws if you get this newer bed. When Prusa ever releases the new part design I will update mine. In the meantime, some hacking required.
I found a way to improve the cooling AND improve the view of the nozzle AND simplify nozzle changes! Win, win, win. Wait! There's more: now with garter screw! What's that? It holds up your sock. Screw in M3x18 to provide light touch to hold upper lip of e3d sock.
One thing that has always annoyed me about the original Prusa printers is the way the part cooling is attached to the extruder blocks the view of the nozzle printing. I can't tell you how many times I have been able to diagnose a bad/failed print by observing how the nozzle is laying down plastic. I also didn't like that you need to partially disassemble for nozzle changes. So I set out to get 360 degree cooling while fixing these problems. I also stumbled on a simple solution for keeping the silicone sock from dragging on the print which has many surprising (not in a good way) side effects.
2/05/18 update: several improvements to air flow, printing, fit, strength. There are reports of the factory shroud sagging from high temp printing. This design is less susceptible due to larger surface area and multiple contact points. Nevertheless, I reinforced and added an optional clip for the back corner. Also built-in supports so no need to add in slicer. Brace is now optional and compatible with my laser mod.
3/20/18 update: based on feedback, improved fit for bed cover, slightly increased PINDA hole, adjusted airflow.
I recommend print in 0.15 layer with 3 perimeters and 40% infill.
First remove factory shroud and fan. Next slide the new shroud up over the PINDA first, then pulling inlet slightly to allow pin to insert into old shroud screw hole. Important to make sure shroud is level. It should be flush with PINDA mount and small circle spacer on other side should be flush with bottom of extruder. You may need to tuck up heater wire and make sure zip tie is rotated out of the way. Finally add clip in rear as shown in photo. Optional, but recommended, use needle nose pliers to add clip in back corner between hook on shroud and x-carriage bearing holder (see photo).
Now screw new shroud loosely to old upper fan hole using M3x10 from original shroud. Next Insert fan outlet into shroud inlet (will be snug) and attach the fan to the mounting arm with hex nuts using original M3x18 screws, loosely. Now go back and tighten all screws, making sure fan stays in inlet. Note that you may need to slacken the fan wire some if you snugged it tight on first install.
Last, you need to replace the factory heated cable cover with the lower profile one supplied here. This should be a straight-forward swap: cut zip, unscrew, pull out filament, insert in new cover, screw down, adding spacer to front screw under bed. Spacer keeps screw tip flush.
[Save this step until you are satisfied with new shroud, and it is optional, but adds garter screw; get this part from my laser mod]. Note when removing extruder cover you may find it stuck. This is due to screw from back side tapping in. You can pry off but be careful. Bonus is this should be the last time you remove it. New cover has clearance built in and installs exactly like original.
NOTE you should remove the shroud if you need to do a full XYZ calibration (rare to never) because without the steel sheet you can rub the back pins.