Love those reinforcements, my friend @eb801!
They will sure provide the necessary solid joint you opt for!
Looking forward to your progress!

LATEST PROGRESS
It's been about 15 years since I last tackled a Classic Airframes model and I have to say, I have yet to pull my hair out or experience a strong desire throw this Wyvern against the wall in total frustration like I remembered feeling about their other kits. This build is actually going relatively smoothly so far, much to my surprise.

I installed the resin cockpit tub and gunsight platform from below prior to attaching the bottom wing/wheel well assembly. Lots of sanding and test fitting required here. Also tackled the air intake openings which took a fair amount of carving and filler and even more test fitting. Next I will attach the windscreen as protection so I don't knock off the gunsight which I have already come close to doing several times.

You're right. After all that fuss making the filter fit, I should have just eliminated it. I will follow your motto from now on. “if you cannot see it, I will not build it…”.
Onwards!

You're definitely living up to your usual standards with this, @eb801

Tom & Erik - yes ,making some serious progress today. Thanks for dropping by.

Wings are now fully attached top and bottom and so are the stabilizers, angled at 10 degrees. Filled all the gaps with more Mr. Surfacer 500 and letting it dry now, so I can add another layer tomorrow. And then a fair amount of sanding and cleanup ahead.

Moving right along Eric. Looking at your exhausts, I recall it was a right pain in the keester to mask off the Sky and then paint the grey.

George - I'm not going to attach the resin exhausts pipes until after all the painting is done. Are they molded in place on the Trumpeter kit?

Ah, those glorious old school limited runs, my friend @eb801!

Fit? Fit? We need no fit!

But, if I am allowed to say, I love those moments that "challenging" kits are put together and come along.

Yes, liquefied styrene might have come handy at those gaps, filling and strengthening the joints at the same time. I usually go with it at nasty gaps and, after sanding, continue with my preferred putty.

You are doing an amazing job there.