As stated by others, it's supposed to be real bad to raise the rear with those cross members. I thought about it too. But I listen to my elders.
I did some work a little while back to replace the mufflers and install a lift kit. I used a 1500 lb motorcycle jack, and a car jack and some ingenuity and it worked but boy was it sketchy.
Obviously, the Tri-Glide is not weight centered front to rear under the engine like most bikes. The butt is heavier and you can't get the jack far enough back to lift it even. Unless you have a super wide jack designed for Trikes. I do not.
What I had to do was place the jack as far to the rear as possible, and then I attached two tie down straps to the front cross member of the jack, the part that sits on the floor with the wheels, and with a tie down on each side I attached them to the floor board brackets. As I jacked up the trike the straps pulled tight and lifted the rear. I used a heavy duty car jack too to help a little along the way, and once I had it up, I used a jack stand under the reverse gear protection member.
Like I said, it was sketchy. But it worked in a pinch. Here are some photos.
Now, just this past weekend I did more work on the Trike (tuner, intake, header and had to remove the mufflers again) and since I wasn't removing the rear wheels this time it was suggested I use regular old car ramps. Mine are 8" tall and plastic. Designed to hold my diesel Ram (8k lbs), bought them at a auto parts place.
I drove it up and let me tell ya, I will never jack it up again for this kind of work (although I hope I never need to again).
I think a regular floor jack in the front would work to make it level and not only would it be more stable than before it would be a lot higher than I had it then. Now, of course, you can get a Pit Bull jack or a table lift. And I would buy a table lift in a heart beat if I had the cash but for basic oil changes and anything else requiring an eyeball view of the engine area, check out your auto parts place for car ramps. If need to remove a rear wheel, you will need to jack it up. I wonder if you could drive it up three? Then no need to jack up the front at all.