Northern Ireland Forests - overnight parking

We've spotted some nice potential overnight stops in NI forests on our travels, but have yet to try any of them out. We've looked into the Tours in the Trees scheme where you can buy an annual permit, on a first come first served basis, for £180. This covers about 15 or so forests, but not Castlewellan, Tollymore, Gosford and a couple of other larger forest camping sites, which are dealt with separately.

Have any of you lovely people availed of the scheme, or have any of you discretely parked overnight in any of our forests and had any bother?

We have a very well-behaved German Shepherd who just loves to play with our 8 year old son and therefore hates to be tethered on a long lead, so what we're looking for are quiet spots where the pair of them can safely have some outdoor play within our sight in the evening and at breakfast without us having to worry about campsite rules or livestock (not that we think our dog would be interested in livestock, but we will not take that risk).

Ally, thanks for this - it's good to hear that TITTs is a worthwhile scheme and we're seriously considering going for it, if there are any permits left. We've camped at Castlewellan a few times through the normal booking process - is the TITTs site there in that little courtyard, or can you pitch up anywhere (within reason). From the TITTs blumph, it appears that you can only park in designated pitches, so say for example, we got our permit and wanted to park up in a quiet part of a participating forest, we couldn't do so; we'd have to stay with everybody else who's staying there through TITTs.
Maybe I should be torturing DAERA with all my questions - you're on a wee weekend away and supposed to be chilling out!

Castlewellan is a different part as Mark has said.

You need to still park in designated bays, but depending when you go you could be on your own. If you subscribe to MHC at the crazy price of £1 a month you could see the discussion in subscribed members chat, plus other benefits.