Hi Loubrey - Sorry I'm a bit late to reply (I've been away enjoying the fruits of my labour)... I've got both auxiliary tanks installed in my 90, both filled from the Mulgo Y-Filler. Daniel installed a stainless junction box in the driver's rear wheel arch which then splits to the two auxiliary tanks. The hose to the passenger tank sits nicely in the gap between the chassis rail and the body.
See this post for some photos. I can send you more details if you require.
http://www.aulro.com/afvb/showthread.php?p=2276418
Filling is mostly easy. Occasionally it gets stuck if you're on a slope whilst filling but a good jiggle helps (wobble the Defender as well).