gnumeric slow with big file

[Henry Proudhon <henry proudhon insa-lyon fr>]

Dear list,

I'm fairly new to gnumeric, and I try to get rid of MS Excel.
I've a quite big files from generated data (8colums, 100000 rows). Later 
on, I want to compile gnumeric with more the 2^16 rows but for now lets 
talk about the first 65536 rows.

Before I was post-treating these files with excel, generating 5 more 
colums with formulas and 2 charts
The Whole file comes to 30 Mo. If I open one of this file with gnumeric, 
the importation is good and take roughly 20 sec.

My problem is when saving in .gnumeric XML format. Once saved the file 
is much smaller (5 Mo) but takes more than 5 min to be reopened, and my 
system is veeeeery slooooooow during this time (I cant do anything else).
I tried to rebuild the file from scratch in gnumeric (importing the CSV 
data and generating the equation again) but it is the same, even without 
the charts.  Moreover, it seems the rows with formulas are the main 
problem: when opening, I cant see in the progress bar that reading the 
file goes quickly (10s) and processing is very long.

Does anybody know a solution for that, maybe .gnumeric is not the good 
format to save (then which one).
Any advice would be appreciated.

Henry