This sounds similar to a problem I had with a scratch built alula style. Do you have a good programable radio and does your DLG have flaps or flaperons? if so you may need to do what I did and add 5 degs of negative flap (flap above main wing) this will stop the wing from rising full force but will force it to level out without stalling at a higher speed launch. Just remember to switch it to 0deg as soon as it's up and stable or you will dive and rise like your porposing and lose altitude fast. Mines on a three position switch so that I can add flap in a thermal. Won't work with yours if you don't have flaps though, if you do and can program your radio, try it.