Well I just had to try it folks!
In preparation for mowing the lawn the other evening I loaded up the JBL and put on an old pair of well tenderized work jeans (on their way to becoming crotchless). After making a critically positioned slit in the rear of the jeans I placed the JBL on the tractor seat, lubed up the nozzle and sat down. All seemed OK so far, though it did take a bit of wiggling and wobbling to get well positioned.
So out of the garage we go, making our way onto the lawn. Engine revving (mine too) blades engaged and off we go! Reaching down between my legs with one hand on the valve and the other on the steering wheel I momentarily opened the valve. What's that I feel? A tickling on the outside of my rectum and a dampness in my jeans?! Some more wiggling & wobbling to try and get a better seal. Valve open again, that seems better . . . oh oh, that damp feeling again. Maybe if I tighten up on the ol' sphincter a bit more... and on it went.
In the end I did get the back yard mowed (and somewhat watered) and I did end up getting probably a quart or so inside me. The main issue was that the jeans were too much of an obstruction to get well seated on the fairly short JBL nozzle and get a good seal. This was not the problem I envisioned when first contemplating this project. I figured that the biggest issue might be ending up in the far corner of the yard when a bad cramp would hit, necessitating a mad dash for the facilities and maybe a big mess.
While this initial experiment did turn out to be a bit underwhelming it was definitely an interesting feeling to be riding around the yard while taking an enema with the neighbors looking on, none the wiser (I hope 😮).
I'm sure I will try this again with some loose fitting shorts, once the weather warms up a bit more. Still a bit too nippy in the evening for shorts up in these northern hinterlands so will have to wait a while for round two.