Knees hyperextend — lock them out anyway?

I'm just getting started with the Stretch series. I'm enjoying it quite a bit so far, but I have a question about the front split.

My knees naturally hyperextend, and I'm unsure whether to full lock out my knee for certain stretches. Over the years, I've received mixed advice about this from yoga instructors or other trainers. What do you recommend? Should I flex the quad and fully extend, even though I'm past straight? I don't currently feel any discomfort when I do that. 

Thanks for any advice you can provide. 

Hi @Charles Fuller,

Yes. Fully lock out/extend your knees even past straight as long that there is no pain involved. Building strong hyperextended knees is normal. (seen commonly in Gymnastics, Circus, Yoga, Ballet, Etc.)