I was thinking one thing here... What if I could take a 3-4" piece of transparend plastic tubing, the kind used for aquariums and similar (not stiff but flexible) - that tube is always flexed because it is stored in circles, right? So, I take some of that tube, seeing that it has a snug fit to the drain pipe (which I could check by inserting the tube from the inside through the hole we all have drilled for unblocking the drain), and when I find a tube that barely goes in - meaning it's very snug - I cut said 3-4" and push it in the existing drain pipe. Not flush with the hole drilled for unblocking but a bit further - like an inch or two further. That way, the said plastic tube would exit the original drain pipe and would get bent downwardss (because it was inserted that way), and since it's a snug fit, all the drain water would go through it.
If anything would go bad, I would use something (a phillips screwdriver) to push the plastic pipe completely through the drain pipe and into the frame. That way, if anything gets too blocked to be cleaned, I could just push it out and be done with it. On the other hand, I'd have a down-bent piece of pipe that would prevent drained water to return and leak inside the cab.
How does that sound? No drilling, just a little game of finding the right dia od plastic tube to insert. What's the verdict here, the public opinion?
Beauty is in the eye of the beer holder
* 1994 ZJ (by VIN) with a 1995 engine (PO knows why)