A lot will depend on the flywheel and to some extent the chucks you have as to how it can be held.
If possible I like to hold on the inner face of the rim as that allows you to get at the most surfaces with one setting but sometimes you can't get the jaws in, particularly if it is a 5 spoke as they don't work well with 3 or 4 jaw chucks. But the usual 6 spoke is often OK to hold with a 3-jaw in which case the inner face will be trued by those jaws. Like this Stuart 10V size one is being held
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This one I used the 4-jaw on as it would not work with a 3-jaw but still holding by the inside so most surfaces can be machined
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Others you may find the inside is not round so you will never get it true, in cases like this turn some of teh inner surface and just like th ehub blend it in, this is a 7" stuart you can see where I have trued it by turning
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And after blending
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Then Paint
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Those insert should hold up OK though if you have a smallish lathe I would suggest the CCGT 060204 as they are sharper so put less strain on the lathe and although meant for non ferrous will work on steel, stainless and iron too. The unbranded ones from ARC are OK, also worth having a look at APT, they do packs of two for hobby use if you want to try them out.
https://www.shop-apt.co.uk/carbide-tips-hobby-use.html
Something else worth getting is one or two of the holders that use the other tow corners of these inserts, that way you get 4 new corners out of them and not two, also being obtuse rather than acute they are abit more durable so good for roughing and use on castings. APT only go down to 10mm square but someone like JB Cutting tools at the show should have 8mm ones
https://www.shop-apt.co.uk/apt-75-scbcrl-lathe-turning-tools-for-ccmt-inserts.html