Should be ok to cut now elms are tough trees, i prefer to make large cuts in spring or summer so the wound has a chance to start healing and compartmentalise. just notice your in latvia, I love that country I'm running low on black balsam might have to visit in winter again still trying to work my way through the whole LIDO menu lol, Have you ever been to the baltic bonsai park in Krustiņi? it was closed on my visits.