I have found the following information regarding the two regiments in question. It would be helpful if you could provide the source of your information.
7 Pułk Ułanów Księstwa Warszawskiego:
At Mir (10 July 1812),: Alexander Rozniecki; brigade Tyszkiewicz.
1 August 1812 in 28 Light Cavalry Brigade of GdB Dominik Dziewanowski (1759-1827).
At Borujsk, Kojdanów (20 November1812):
Bio Dominik Dziewanowski:
Bio Augustyn Zawadzki:
7eme Régiment de Chevau-légers Lanciers:
"In the end of August 1812 Colonel [sic] Józef Boguslawski and 60 lancers joined the 1st Light Cavalrymen Regiment of the Guard as the 11th (a la suite) company and fought in Russia. In December the lancers escorted the Emperor from Smorgon to Oshmaina. There they met the squadron of the 7th regiment commanded by [Ignacy Ferdynand] Stokowski that joined the Great Army after crossing the Berezina in the end of November. Later on both units were under the command of General Latour-Maubourg who was to cover Vilnius. At that time Stokowski's lancers were the only cavalry unit beside the Guard's Light Cavalrymen left by Napoleon at the disposal of Marshal Murat." p. 267, Wojsko Polskie w służbie Napoleona - Legii Nadwiślańskiej i Lansjerom Nadwiślańskim (2008).
Kirkor - "Legia Nadwislanska 1808-1814" p 324:
"On 16th September 1812, Chef Cotty [i.e. chef d'escadron Coti of the Red Lancers] with 60 veterans Vistula Uhlans and 70 young Red Lancers scouted on the road to Borowsk. Cotty's force was ambushed by Cossacks, they were attacked in the wood from both flanks and rear. The Poles and Dutch were routed. Boguslawski was furious with careless Cotty and his lancers. The heated exchange of opinion ended up in a duel."