First I don't have any seed for you sorry my tree is not big enough.
Second there are 3 different populations (in Texas) of Acer grandidentatum one is in Ft.hood another in the Hill Country around Bandera (Lost maples area) these two share
similar genetics to a Chalk Maple Acer saccharum var. leucoderme). (Acer saccharum var.grandidentatum) which is what most people have in central Texas. (Acer grandidentatum var grandidentatum) is
in the Guadulaupe mountains and reaching as far north as Utah and as far south as Northern Mexico.I have a Acer saccharum var. leucoderme which was collected in east Texas and has performed well in my Alkaline clay of Austin.My point being you may be able
to find the Chalk maple seed easier. The seed also needs cold to germinate typically moist stratification for 90- 120 days @ a temperature of 33-39 degrees.Many of these seed will not have a viable embryo. Put the seed in water if they drop to the bottom that is what will germinate @95%. Discard the floaters.
Art
Q