Looking neat

love your coupe, looks like it has loads of grunt! how much power is is making?
your vids are a joy to watch

It is fun to drive, I know there is more in her with a better setup (Rear end has too much roll).
Fix on the way....
Car makes around 300rwhp, remember it has a 36mm restrictor - (I know the exact figure but that's a good enough estimate )

Developing a simply CA head drain, using the rear welsh plug to tap in a 7/8" UNF (-10 AN thread) thread into the welsh plug for a oil return, push back in, seal with a ORB to AN fitting and weld on a AN fitting to the sump, simple (rear welsh plugs are 25mm if anyone is interested, pretty common). You could tap a 1-1/16" UNF directly into the head which would be a -12 AN thread fitting, but I didn't want to modify the head without trying the welsh plug idea first (plus I have a 7/8" UNF tap but not a 1-1/16" UNF)

Nice set up. Don't stiffen rear too much, might loose traction under power

yeah agreed, I initially thought I would be ok with the rear really soft and started out that way racing, but the amount of body roll in the rear is becoming problematic. If I need to balance it after I install a rear ARB, I can make front changes to rebalance or re-assess.
There is nothing crazy about the setup, more following others who have been down this path. Their decisions support my calculations, which is always nice.

Yep- why reinvent the wheel. Just make yours faster

that's a pretty good analogy for this form of limited modification motorsport...
Probably the only significant difference that comes into play these days is the lateral G is creeping up with the grippier tyres, not uncommon to get past 1.5g lateral now.
With everything beefed up in the rear, I run out of suspension travel pretty quickly.

leave the springs and maybe you can use a swaybar , if the pic will load here is a unit I make for the rx7's

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I have this setup to return excess oil buildup in the head.

http://imagizer.imageshack.us/v2/320x240q90/20/4n53.jpg
http://imagizer.imageshack.us/v2/320x240q90/547/rnve.jpg

Wards,
That looks like a very nicely made rear ARB. I will be adding one very shortly. I suspect one of your quality would be slightly out of my price range however.
Not looking for anything fancy at this stage, get something in place which is close to what I need size wise and upgrade as needed in the future. K-mac sells a "bolt on" kit that seems like a good starting point.

Worsel,
I was only going to tap the exhaust side due to the way the engine leans.
My initial try is going to be to tap a thread into the welsh plug (I know it is thin but there isn't any pressure on the line. Use a ORB fitting and plumb back into the sump on the oil filter side. I have modified my sump to add 2x gates to stop the oil for surging to the back under heavy acceleration. Hopefully this will stop the surge issues am having. If you wanted to modify the head then a -12 AN fitting can be taped into the welsh plug hole (25mm Welsh plug). a -12 fitting is actually a 1-1/16" UNF thread, these taps are hard to come by.