While not a frame builder yet, I have built a lot of things over the years (included hacked roller set up so a luge sled could be used for training on roads).
My concern, especially i used for skate style vs classic nordic style, that there will be a lot of lateral forces in play, and with the amount on length added to fit the larger wheels that unless using really thick plate, there will be way to much flex, especially with 16 in wheels
maybe flat, with stiffener welded on outside, but that sound's like it is going beyond OP's current shop toolset
Doesn't hurt to try,
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Life is too short not to ride the best bike you have, as much as you can
(looking for Torpado Super light frame/fork or for Raleigh International frame fork 58cm)