No, add enough tongue extension to get the transom close tot he rear of the trailer; don't just extend the bunks back. Galvanized doesn't matter when welding, just paint it all to match or just for protection; galvanized and non-galvanized will weld up together just fine. Take a look at some of the trailer builds on this site to get a good idea of what you need to do.

In the image below I added about three feet to the rear of my trailer as well as dding three feet to the tongue to get the hull to fit correctly. Where the bunks end is about where you want to be. The main thing is to have the weight on the transom, not the thin skinned hull bottom.

So, extend the tongue up about 3 feet. Then fix the bunks appropriately.

Thanks for the help

I'd go 4ft. It will be one less foot you have to back down the ramp to load/unload. The bow stop could use some more space between it and the hitch. If you don't have considerations such as storing in a garage for clearance issues, the longer the better in my opinion.

Then I will just do 6 feet then, because I do agree that I need more room between the post and the hitch. Plus, it'll be possible to open the tailgate of our truck. Sound good? Will the added length aggravate the tilting feature?

Just kidding haha

I'm gunna go 4 feet, I still want to be able to fit it into my garage.