Old town 174 question

I’m an amateur canoeist, just joined the message board. I just purchased an older Old Town 174. On further inspection I noticed the hull has a rather large soft spot in the middlle that flexes easily. My 169’s hull is definitely not like that. Is this normal, or something I should worry about? If it isn’t normal, is there a fix, and how do I go about fixing this. I read on a different site that the soft hull is so the canoe can slide over rocks easier? I haven’t put it in the water yet. I’m going on a three day river trip, and plan on letting a friend use the 174. I’m concerned the soft spot will effect performance, or at the very worst crack and leak. Any advice or info is greatly appreciated.

On mine
I considered it normal based on the size of the boat.

Common in older, long, plastic canoes
"Oilcanning" is not desirable but it is common in that kind of canoe. The plastic is very tough, so it’s unlikely to crack unless it has suffered a great deal of impact or abrasion damage.

You can diminish the oilcanning by putting your heavy gear over that spot or, if no gear, by jamming the right size foam slab under the center thwart as a brace.