Venom II / Taipan Serpent - Anyone own one and have feedback?

Finally getting back into the swing of R/C after 7+ years of things sitting on the shelf, begging to be flow.  I have a Black Widow that hasn't been used in years up until a week ago, and it's having a few issues sucking fuel (about to pull it apart to clean it out)... but even back then it had some trouble lifting my Ace R/C Ace High MKII powered sailplane off the ground... partly because it'd been rebuilt a couple times over the previous past 5 years of abuse I put the poor thing through while learning to fly.

Anyhow, I got to looking around for rebuild parts for the Black Widow, and came across coxengines.ca and exmodelengines.com.  Looking around the forums here, looks like the guys at both places are pretty reputable and friendly, so I thought I'd give one of their custom engines a shot, and see how well it worked.

My question is, has anyone bought a Venom II or Taipan Serpent, and how well do they perform? Is there a significant power difference between them and the Black Widow?  Further, I see the Taipan Serpent uses a different, insert-style glow head - how well does this glow head compare to the stock head?  Guys at EX Model Engines and Cox International, I'm happy to hear from you too.  Just wanting to see what may work out best for my MKII