I have used the gel type batteries a couple of times and I had poor luck with them. For me they always failed early. I suspect it is our voltage regulators allowing too high a voltage and damaging them. Anyway, I now use a standard battery. The other day my Volvo battery died. It is located in the trunk. No rust. Trunk is perfectly clean. The battery has a tube that vents the gasses below the car. I have read so many threads here on batteries but I don't ever recall anyone suggesting one of these batteries. Not so special really. It is just the filler caps are sealed with a vent hole on either side. One get plugged (supplied) the other gets a plastic 90 also supplied. Simply run a rubber hose under the car and done!

That would probably work just fine. Most people today pay attention to the weak spot of the car and most cars aren't driven much in the rain.

The issue was the rain would wash down over the battery and pick up any acid that leaked out. I'll bet your Volvo trunk is dry. If our batter tray was dry I'll bet there would be less of an issue.

Correct except water is not an issue because no acid ever is in top of the battery! it is all vented. Rain would no longer be an issue