I had an online chat with Mark yesterday, he has "a good stock" and agreed with the 1440 recommendation. You will need to remove the collar from the drive shaft that you presently have between the strut and drive dog. The 1440 is much longer than the Dumas plastic prop, so it will need more shaft length. The other thing about Mark's props is, as I said, he's done all of the prep work. If you order one of his props, you just install and run. If you buy a raw prop, you would need to sharpen and balance it before you can use it, a long process that requires some special tools, a dust mask/respirator and lots of practice.
As for the clear cover on the radio box, it is a good idea for several reasons:
- it is considerably lighter than that low quality plywood cover
- it lets you see what the radio gear is doing if you're having control issues
- it won't absorb water through the screw holes, which you won't need to drill since it will be taped down instead of screwed
Lithium based grease is commonly available at auto parts/supply stores as well as box stores like Home Depot and Lowes. What I use is pushed in with a small grease gun but, in your case, that might not work. WD-40 has a lithium grease in a spray can that has a tube you can use to fill the stuffing box and strut.