a big company such as evenflo, ect spends alot of money on safety issues therefore if they are saying it(most excersaucers say it right in the manual) then i have to think there are problems by doing so. why risk it, kwim/
oh wait, just found this, someone posted this as a response they got from evenflow when asked about the harm of flatfooted-
"Hello,
Thank you for your inquiry regarding the Evenflo Exersaucers.
When a child is placed into the Exersaucer it is advised the child not be flat footed. The recommendation is for a variety of reasons. The Exersaucers are capable of rocking; when a child is flat footed the momentum a child is able to get is more significant when flat footed versus on tip toe. The child has more balance when positioned flat foot which can make it easier for a child to tip the Exersaucer or climb out.
Children who are in the Exersaucer are not capable of walking yet, therefore full body weight is not recommended on the child’s legs when a child bounces/jumps. When the child gets excited or stimulated by the toys a child will often bounce or jump. The impact of a child’s full body weight coming down from a bounce/jump is not being caught by the Exersaucer springs if the child is placed in the Exersaucer with flat feet.
I hope the above information is helpful in explaining why a child is recommended to remain tip toed while in the Exersaucer.
Thank you for contacting Evenflo. I appreciate the time you have taken to email us.
Amanda Penny
Senior ParentLink Representative
Evenflo Company Inc."
but i have a solution, did you try on of those doorway jumpers, i have one where its a little tray going all the way around the baby, and a little music plaything, with loops to attach toys. your son would be able to jump around, you can change the toys, and move it from room to room. these are completely adjustable(at least mine is) so there is no fear he will outgrow it.