Hi Avolpe

Yes it is possible, you will need to edit the Summary ASP page for the custom entity to include the table that you want. For example here is one I did for a custom entity in my own system. 

At the top of the ASP page I edited the section that looks what to get and where to put it, so I added in a bit that references the custom table and then added in the line to then return it to the screen 

Very cool, this works well! The only question i have, is there a way I can limit the number of rows that list displays? I am trying to add 3 blocks total to the bottom, so I don't want them each taking up to much real estate. Can I do that this with code?

yes you can.
e.g. StockLevel.RowsPerScreen = 10;

Does it matter where I put it? I have tried it in a few different places and it doesn't seem to be taking effect.

<!-- #include file ="..\crmwizard.js" -->

<%

if( CRM.Mode != Save ){
F=Request.QueryString("F");
if( F == "ItemsNew.asp" ) CRM.Mode=Edit;
}

Container=CRM.GetBlock("container");
Entry=CRM.GetBlock("ItemsNewEntry");
Entry.Title="Items";

Container=CRM.GetBlock("container");
ItemCRMQuotes=CRM.GetBlock("ItemCRMQuotesBlock");
ItemCRMQuotes.RowsPerScreen = 5;
ItemCRMQuotes.Title="CRM Quotes";

Container=CRM.GetBlock("container");
ItemInvoice=CRM.GetBlock("ItemInvoices");
ItemInvoice.Title="Sage 100 Invoices";

Container.AddBlock(Entry);
Container.AddBlock(ItemCRMQuotes);
Container.AddBlock(ItemInvoice);

Container.DisplayButton(1)=false;

...

Don't repeat the Container=CRM.GetBlock("container"); - you only need one.

From the CRM developer guide:

RowsPerScreen
Sets the maximum number of rows displayed on each screen.
Use this property to limit the number of rows displayed per screen, and then use the forward and
back buttons to display next or previous screens. Each user has a Grid Size setting in their
Preferences. This setting overrides the RowsPerScreen setting except where you're using the
ListBlock in a CRMSelfService object.

So it appears that this property can't be used to do what you want.