Super-size my pre-boil gravity

Hi. I'm planning to brew the Imperial IPA Pliny clone from the pages of the BCS. It wants an OG of 1.080 and Beersmith estimates my pre-boil gravity will be 1.065. That's about 8 points higher than the most I've pulled out of my tun.

I mash in a 40L Gott-style cooer with a stainless steel, braided-hose ring at bottom. I've calculated my mash efficiency at about 73%. Beyond pH, which I've already covered -- I hope -- with pH 5.2, are there any tricks I can do to get a higher pre-boil gravity? I've read about adding more malt than is called for in the recipe. How much more? I've also read that you can throw in more after you've started lautering, if you find yourself coming up short.

Thoughts?

I did some tests with changing my lautering prosess.

After mashing I pump away 70% of the wort into a separate container. I slowly lauter the grainbed with the amount of water BS indicates and start circulating for 40min at 78C (grainbed).
Compared to my original technique, where I did not pump away 70% of the wort, I hit a 2 points higher Pre Boil Gravity.

Regards,
Slurk

What is your batch size?  What is the highest gravity (pre-boil) that you have accomplished so far? 

If it is well beyond what you have tried before, I would lean towards doing a single infusion with no sparge.  Count on a loss of about 5% + in efficiency and make your grain bill to match that. 

Other options available:  extend your mash time to 90 minutes and give your sparge a much longer time to drain (assuming a fly sparge).  If you batch sparge, then allow it to sit for 20 to 30+ minutes before draining to give as much time as possible to extract remaining sugars.

Lastly, have some DME on hand to make up any difference from actual results to expected results.

It's a 5 gallon (19L) batch. I didn't read my notes carefully enough. I thought the highest pre-boil gravity I had was 1.057. Actually it was 1.064, only a point away from my target for this brew.

I do a single-infusion batch sparge ... but this time could up my grain bill 5% and extend my mash time. And DME is indeed an option.

This is (a similar version) of the first all-grain recipe I brewed a year ago. Everything, everything went wrong with that brew, but it nonetheless turned out not bad, if nothing like a Pliny clone, or even like an imperial IPA for that matter. So this time I'm overly anxious about hitting numbers.

Sounds like it is within your present capabilities.  Good luck with it!