As you may tell from my avatar I'm a child who grew up watching a certain cartoon featuring the great voices of David Jason and Terry Scott (I'm ignoring the more recent reboot). I felt the presence of a whole road named after the luckless sidekick too great an opportunity to pass and managed to find somewhere to pop a small cache, which also neatly filled a gap between a couple of others. Tweezers will be advantageous here.
I would highlight that Penfold Drive itself is private land and there are numerous signs stating that if you park on it you're agreeing to paying a hefty fine. You also can't stop on Harts Farm Road. I'd therefore suggest parking nearby and walking over - the nearest would be the car-park for Ketts Park so you could have a nice walk around the park too and find the other caches there. Alternatively you could go shopping and include a stroll in your visit! It's also on the cycle path so biking along is an option.