Hmm, didn't think about doing it that way! Is there a brace under the top seat holder board?
I have seen lots of people adding some sort of clamp to theirs but that is an added expense. Yours looks like it cost less than $8!!! That would be me being generous with the price of 2x4's mind you!
Lately, I have just been using my 7' ladder. Basically, I just spread the legs apart and hang the seat on the metal hinge bar with the bike passing under the ladder. It works but does not give the best access to the bike. But I've had the ladder for at least 8 years now so I will consider the bike stand mod as a freebee!!!!
I have an old style slider to transport my bikes and use to just hang the bikes off the end of my Jeep to work on them. Well I tired of that; and scrounged wood to make this ghetto stand. I still use it today..
1SPD. i just cut a notch in the 2x4. the seat post slips in there so it doesnt slide around on me to much. Its good enough for washing and cleaning the drive train. Ive got some ring nails holding it all together.