Coil spring spacers

I'm due to have a full front end alignment and possibly offset castor bushes installed next week in Adelaide. I was thinking of getting them to whack in a set of 4 x 30mm coil spring spacers (those donot shaped doo-dads that jack-up the truck's height without changing the coils).

Has anybody on here used them? I am interested to know of any downside to them. I already have very heavy-duty Lovells springs (4" front and 5" back) which give me an overall increase of about 90mm front and back due to the 3+ tonne my vehicle "normally" weighs. It's interesting that when I do load up for a trip and chuck the camper on the back, the height of the vehicle drops about a half inch only; I've only been able to measure this by line of sight recently, following the addition of 3 large mudflaps at the rear of the Patrol. At normal (b4 loading etc) they sit about 1" above the ground......whack all the gear in/on the 'trol and they are about half inch off the ground. I guess the polyairs are also partially responsible for this situation.

Thanks in advance for any feedback you provide.....

Cheers

Roachie