dublinpilot
A windscreen attached aerial should be fine too, if the aircraft has a windscreen which is almost horizontal near the top edge - like a PA28 I used to rent.
The key is to give it a good view of the sky.
Not as good as one on the top of a metal roof.
If I was renting out a plane, at say £100/hour, and getting a gross income of some £10k-£50k a year, I would spend £300 to reduce the chance of a renter getting lost, because if one of them does get lost then *he* might get done by the CAA (or better still the DGAC) but financially the buck will stop with *me*. If the plane gets confiscated in some 3rd world country
the renter will just jump on Ryanair to get back but I will have to retrieve it. In fact, if I was renting out a plane, I would fit a really good panel mounted GPS in it, and I would make sure everybody who flies it knows exactly how to work it.
You might try making that point to the owner.
I accept that some people prefer to use a stopwatch etc and they can just turn the brightness right down so they can't see it, and turn it back up if they are "temporarily uncertain of position"