Porsches have very few, and specific jacking points. This Model T is even lighter, so I'm wary.
It has always been my understanding that the center of the front axle is fine. There are two schools on the rear axle - one says that you should never jack it at the center of the axle (i.e. under the "pumpkin") and the other school says it doesn't matter and "I do it all the time."
Others will say not to jack it up the middle. I've always done that way, and my father before me. Have yet to bend one.
I jack the rear axle at the center also. But, my cars are 1921 & newer. I would not jack a 12 rivet rear end or earlier at the middle. (Your car does not have a 12 rivet rear end and should be fine to jack in the middle, though again, others will say not to.)
Model T Rods
1. Chock both rear wheels
2. Raise front until oil runs back into hogs head
3. Disconnect battery
4. Loosen bottom inspection pan bolts and let oil drain from dips
5. Remove inspection pan and complain about the mess. Take a picture & a Sip of cold beer, and go post comments about how loose the rod caps feel
6. Find 5/8 socket with elbow, cotter pins, and cotter pin removal tool
7. Note one file mark on rod cap #1, facing cam. Remove and adjust one rod cap at a time. If no shims are left, decide whether to file cap or order new rods, or both. Be sure there's enough babbitt material left not to damage crank.
8. Remove enough shims for rod not to slide forward and back without help from a tool.
9. Call yourself a tool for not ordering new rods yet.
10. Tighten & reinstall cotter pins
Always look at the babbit on the bottom of the rod above the crankshaft. It wears out faster than the cap. If it's cracked or worn through, you need to re-babbit.
Also, find a 9/16" socket.
An ideal clearance should be .0010/.0015. At that clearance, rods will move fore & aft. Fore & aft is no test of rod clearance.
If you tighten the rod cap down on a piece of newsprint and find it tight, then remove the newsprint and it now moves back and forth, you've got it right.
Answer to the original question: It's probably OK, but why take the chance that it isn't? Better safe than maybe bent. Same deal for the rear. Under the pumpkin is probably OK, but why gamble?
I think you better finish numbers 11, 12 and 13. Put the pan back on, reconnect the battery and put oil back in.
Back to the original question. Don't crawl under the car when it's on the jack. You should put jack stands under each end of the axle near the wheel. With a hydrolic jack, it's very easy to jack up one end at a time. I personally don't place the jack in the center. Only takes a minute or two to jack up one wheel at a time.
Steve, I hope you do what the label on the jack says, and wear your safety goggles when you raise the car!