Trailer Height above ground

HI Guys,

I have come to the conclusion as my family begins to grow (kids get older) the more crap we need to take. I recently loaded the old faithfull 6 x 4 but she was struggling to hold it all.

I am now going to build a new tandem trailer to hold it all, eventually motorbikes will need to come etc so i will plan for the future. My wife recently convinced me to buy her a new tent which we now have a huge canvas tent (must admit i am pretty happy with it) so there goes my camper trailer idea.

We have an R51 Pathfinder ST-L with no lift etc (yet). I want to mount a water tank under the trailer, what is the ideal height of the trailer above the ground? Do i need to put 4wd suspension under it or will rocker suspension with 16" Sunraiser or similar give me enough height as to not damage the tank when going off road a bit.

I have very little experience with a 4WD so where we go are not very difficult drives. But I would to be able to do the odd river crossing etc and try to limit the amount of water to get into the trailer and wet out stuff.

Am i dreaming or is this trailer setup possible. I have fitted the tank under my 6 x 4 as a temp measure but it does not have the best clearance.

I suppose dragging a large tandem is not conducive to 4wding but i doubt very much I will be doing anything too difficult.

Also off that topic, how do people go about leaving there camp site to drive tracks during the day. I would prob put my fridge back in the car but what bout other things, my concern would be go for a drive and find everything gone, etc jerry cans, kids bikes, chainsaw etc.

Thanks Bruce