no, there is no shortcut;
UP will arrange the mod files differently, packing most of them into sfs file format;
besides, 4.09m is a different beast than 4.09b
best idea for you would be to back up your old running install, then delete the mods and the files folder and make a clean install of 4.09, the skins for it and UP1.8 in a temp folder;
then copy over the files from the temp folder and run 4.09m with UP1.8
if everything is running, and it should, then you have a working great UP1.8 install and will be ready for any future campaigns, be they for mods or for a non mod install;
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Experience of battle divides those who talk about nothing but the anticipation from those who talk about everything but the memory of it.