It makes a fine container plant. Be sure to use a big enough container, a high-quality container mix for your media, and plan on burying the container in the ground for the winter. In general, you lose 2 zones of hardiness above ground, and you're already at the cold end of it's hardiness range.

I'm going to offer a different opinion :-) Japanese maples are in general immensely suitable to growing in containers - I grow ALL of mine in containers and there is considerable discussion on the Maple forum regarding container culture of these trees in all sorts of climate zones. Obviously, in colder zones, some sort of winter protection is desired but in zone 8, it is not necessary. (most J. maples are fully ground hardy to zone 5 - I know of none that have only a zone 8 or 9 hardiness rating). We had winter temperatures this past December that dropped into the single digits - unusual for a zone 8 - and all my containered maples were fine. If you have poor soil conditions, bad drainage or the presence of verticillium wilt pathogen, growing Japanese maples in a container may be the most reasonable course of action. The size of the container is dependent on the size of the plant, but I'd suggest at least a 24" box (or the container equivalent) for long term container culture of a JM. And pay very close attention to your potting medium. Japanese maples prefer a very well draining, chunky (aerated) potting mix that is on the acidic side. You will also need to pay close attention to watering and fertilizing, as you would with any plant grown long term in a container. And periodically, these will need to be unpotted, root pruned, the soil refreshed and repotted. It's not a plant and forget situation! 'Crimson Queen' in particular has an ability to develop some serious width - at a previous nursery we had a boxed mature CQ that was 9' across! Plant tag info on height and width are estimates and often, only estimates for a 10 year growth period. When in doubt, allow extra room so the tree will not interfer with any structure or walkway, as you don't want to prune constantly to keep size in check. Height on either of these should not be a concern - both are relatively low weepers. But they do grow into mature trees with a lot of sculptural interest, so placing them where they can be seen and admired in all seasons is preferable than squeezing them into a foundation planting situation. These are specimen trees and deserve pride of place.

1) I can't think of a single tree you can't grow in a container if you're willing to provide favorable cultural conditions for it, so go for it - have some fun. You may wish to consider cutting the 4 ft trees back to a low branch that favors the vertical though. You could also remove branches & leaves from the existing trunk in spring and use it as a stake that you can tie a branch that already favors the vertical to. Once the branch is 'set', you simply cut off the trunk above the new leader. This process will give you a shorter and bushier tree in the end - perhaps more suited to container culture than a 4 footer. 2) The trees will prefer a mildly acidic soil, and sandy soils are usually on the acid side, so my guess is the trees will do well as long as you can keep the moisture supply adequate and make sure the nutritional needs are being reasonably met. There is no reason you cannot successfully cultivate J. maples in in containers and maintain them for years and years - with a little attention to the pruning of roots as well as above-ground parts. Al

In western Washington, Bloodgoods (true Bloodgoods, that is) can get quite large for a Japanese maple. I've seen them at 25+ feet. But that takes decades and they won't grow that big in a container. Even so, a Bloodgood of any reasonable size would be a bear to repot and root prune. IMO, not at all the best choice for a container. Especially if this is your first attempt at growing trees in a container. Truly, you want to start with something smaller. btw, NO Japanese maple gets "freakishly tall and huge" :-) They are usually considered to be small to mid-sized trees.