The tubs are pretty tight, theres about a 4mm clearance atm without the flexwatt, i'd be damn impressed if any royal could get through that . I basically judged by eye as i was building, i built from the top shelf down so basically i filled the rack upside down, placed a tub on and then a shelf, marked where the shelf came to measured 5mm and drilled holes. Seemed to work fine.

Well the sides arn't that flexible but i countered this is 2 ways:
1st) i made the rack wider than the tubs, even i can't bend them enough to get into the tub without moving it.

2nd) the divider is screwed it, as shown in the pic below



So the sides of the tub are basically screwed in place, i was thinking for a bigger snake though you could just use a strip of wood just screwed to one hole (so the wood would be 25mm x 25mm x tub width), so the snake could pass freely around the whole tub (underneath the 'beam' of wood) but also the sides would be solid.

Dare i say it atm i think its escape proof, but i don't have a very large snake to test this. BUT the tubs can easily be lifted higher by getting 2mm think plastic from a hobby shop and cutting feet for the tub.

The rack is 1220 mm high, that includes a storage shelf at the bottom which could easily have another tub on it, it comes to the bottom of my ribs and i'm 6' 1". Its basically 200mm a shelf, so you could easily have 7 if you built it virtually on the ground.

I went on the open plan rack for two reasons:
1) I also read what adam said, which was good enough for me.
2) it was cheaper to build (probably not to heat though ).
3) It looks nicer, in my opinion.

I'm going to wait awhile on the flexwatt, amek sure i get exactly what i need don't want to end up paying more shipping because i forgot something! I've got no rush anyways its going to be at least 2 months before the CITES paperwork it done, then depending on money i might have a balance to pay off aswell.

That sucks on the B&Q front, my local is a trade store so its the size of a aircraft hanger .

Graham