Frame Stiffing to reduce Porpoising?

Grit dog wrote:
Still not a chance in heck that that truck has anywhere near a 5klb payload rating. Irrelevant of the reduced TC weight ratings that the mfg provides.
What’s the door sticker say? I’d be very surprised if it didn’t say 11,200lbs gvwr.
I understand you want to make this work but ignoring the obvious like actual gvwr and questions/suggestions about your suspension (You’ve only said you replaced the shocks. Which is only a small part of the equation) shows that you’re trying too hard to make this work by ignoring the factors you choose to not consider.

So until you post a pic of the gvwr proving that your truck is somehow special compared to the other 100,000s that went down the line those few years, you’re just kidding yourself.
And I’ll eat my words as well.
The other difficulty is sure some of these major mods are possible, however you’ll be hard pressed to find a shop that will take on the liability of any major structural conversions. And those that do will charge about as much as buying your whole truck again. Maybe more.

The only recent comparison for frame mods is Mega cab long bed conversions. And years ago those were about $5k byob (bring your own bed). What you’re proposing is of similar risk and complexity minus the frame stretch.

While my responses and others seem harsh, or condescending it’s your truck and you asked the question. My intention is never to mislead which is consistent here as well.
Good luck.

Gritdog your post is exactly what you said it was, harsh and condescending. I'm not offended by it but I question why you feel it is necessary to the point of stating it yourself.

Moving along, you aren't answering my original question. The only question mark in my first post is for this sentence:

"Has anyone else gone through this or found a way to handle excessive porpoising on older C channel frame trucks?"

I assume your point is, your camper is too heavy for the truck. If you want to go by stickers on the door, that is fine, you probably are correct depending on how much gear is loaded. But I didn't ask about the sticker on the door nor was I asking if the camper weighed too much. I asked if anyone has ever gone through the effort to stiffen the frame.

From the answers so far, it appears the answer is no. I appreciate everyone's response as it tells me it is uncharted territory and if I do proceed, I should proceed with definite caution.