I don't know about martagons, but I have 3 Black Beauty that may get a little more sun than you are describing. They will bend right over; the upper part of one is horizontal to the ground they bend that bad. Another one, Red Velvet, gets a lot of sun and still bends over really bad, rather disappointing. They get very tall and need to be staked with tall stakes.

I saw a photo of a huge clump of Black Beauty when I ordered mine. They must have gotten full sun and could help support the others some but seemed to be growing nice and straight.

Lilies need almost absolute full sun to do their best. The ones that get the most sun lean the least, but none of mine get full sun all day.

The only lily I have that grows tall and perfectly straight in part shade is Mrs. R. O. Backhouse. It has tinier flowers but is quite charming, look like little lanterns. It produced a lot more flowers this year but has yet to show any sign of multiplying.

Don't have the true tiger lilies personally (they grow wild here and are the ones with the little bulblets or whatever they are called, helps them repro faster, NOT the ditch lilies which I don't like). Anyway, when naturalized in mass plantings, they don't look too bad leaning, looks rather nice actually, have posted this photo before. One nice thing about them apart from covering difficult spots is that they get so thick they tend to crowd out most weeds and grass and require no care whatsoever once established. When not blooming, the foliage looks better than bare, tall grass or whatnot.

Where I saw these they are on a northern exposure slope, entirely covered with them for many square yards, and they all lean out enough so they can catch the eastern and western sun, really a pretty sight. I had asked for some, the husband said I could, wanted to wait until fall to dig about 6, then there was an issue regarding me, and they were all sprayed, hardly one left. Couple years later, they are all back better than ever. I'll get some from someone else or buy if I figure out a good place to plant them where they can spread.

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Nice picture! I have two gallon pots of those orange tiger lilies right now that I need to stick somewhere in my garden. I don't really have full sun either...

I can relate to that "stick somewhere" lol. I think they would do well on my terrace but not sure I want them to take over. They can be controlled, just happened to go by where I took that photo, and there're just a small patch of them blooming now, not so much coverage.

If they're happy, they will surely overpower other plants except possibly trees and shrubs.

I stuck them behind a Spirea 'Magic Carpet and in front of a fence. I've got a Clematis 'Daniel Deronda' nearby and the purple will look nice with the orange. The Spirea has varied orange, yellow and green foliage and magenta flowers. It will be a colorful corner.

I wish I could see a picture of it when they bloom next year with the other plants. It's funny, but I used to have a thing about colors. Now I'm a little more flexible and put colors together I wouldn't have tended to when younger and like the results, blue and yellow, orange, pinks, purple, nice combos.

Martagons should be fine with the amount of light you describe. Mrs. R.O. Backhouse is a martagon as well. The tigers will likely tolerate those conditions but will probably lean. Black Beauty can have 30 or more blooms on a mature stem so will likely need staking in those conditions. The only way to know for sure is to try one. If your sun is quite intense it may be enough and they may actually appreciate some afternoon shade. In my zone 4 garden they appreciate more sun. Just another note: tigers carry a virus which can be transferred to your other lilies. They should be grown well away from other lilies. If I remember correctly, they should be at least 100 ft. from other lilies.