Staking the stems firmly is one way to deal with thin stretched stems. Now that the plants have adequate light, the stem will fill out and will soon be able to support the plant. Your friend's idea to plant the stem deeper so that it doesn't have to support weight for as long a span is another good way to solve the problem.
Readers with grow questions (or answers) should send them to Ed at: Ask Ed, PMB 147, 530 Divisadero St, San Francisco, CA 94117, USA.
You can also email Ed at AskEd@cannabisculture.com and send queries via his website at www.ask-ed.net.
All featured questions will be rewarded with a copy of Ed's book, The Big Book of Buds. Sorry, Ed cannot send personal replies to your questions.