Uhhh I don't know if they are good. I'm sure they fit but according to my thinking and what my mum said to me, the t tube is weakened if you use a bike seat post. The reason is because its too short.
If it is longer, its fine but I don't think its that long. I wanted to cut part of the handle bar to use as my fork reinforcement. I told my mum and she said if I have a part very strong and not as strong, the not as strong one will break very easily.
I don't see a reason for using a seat post. Uhh its weaker because it cannot go all the way down to more or less at the bottom of the t tube which means the bottom is weakened.I don't see a point of using a seat post. You can use it and put reinforcement at the bottom of the t tube also but thats if you really want to use a seat post. I won't want to use it as I see no help in it.
I may be wrong but just trying to give you some things to consider.